RED FLAGS and red faces were the story at the season's halfway point, as the Eagles stumbled last night when given the chance to take control of the NFC East.

The Dallas Cowboys were tougher in the trenches, sharper and a little luckier in grinding out a 20-16 victory at Lincoln Financial Field that put them in first place in the division at 6-2. After opening their divisional schedule with a pair of solid wins, the Eagles sit at 5-3, as big an unknown as they were when the season started.

"There were some things that were very close that I felt could go either way, and they didn't go our way," Eagles coach Andy Reid said.

The pinpoint offense that dominated the Giants last week was nowhere to be found. Donovan McNabb was back to looking harried in the pocket and uncomfortable when flushed out of it. He ended up 16-for-30 for 227 yards, four sacks, a touchdown and two picks - McNabb's first multiple-interception game since Baltimore last Nov. 23, when he was benched for the second half.

For Eagles fans, the unpleasant surprises began before the game, when the Eagles announced Brian Westbrook among the inactives, after the franchise back got a headache Friday afternoon, reviving fears that Westbrook was not over the concussion he suffered against the Redskins 2 weeks ago.

But the Eagles still took the lead in the second half and seemed capable of winning without Westbrook, until suddenly, they weren't.

The game turned when the Birds couldn't gain a yard on second, third or fourth down from the Cowboys' 45, the score tied at 13 early in the fourth quarter - at least according to referee Walt Coleman's crew. Reid challenged the fourth-down spot, and seemed to have a good case on replays, but the challenge was denied and Dallas quickly scored a fatal touchdown.

Reid said he couldn't comment on that or his previous lost challenge, the more understandable decision that LeSean McCoy's momentum carried him back behind the first-down point after McCoy caught the ball at the stick, "unless you're willing to pay for it. They go the way they go."

McNabb stressed that "there were too many penalties, too many miscues on my part, too many miscues by the offense," regardless of the calls on McCoy's third-down plunge and McNabb's fourth-down sneak; the Eagles thought they picked up the first down both times, but especially on fourth down.

"I felt like half my body was past the marker," said McNabb, who slid forward on the backs of his linemen, but somehow was granted virtually no forward progress, though his line was not pushed backward, on fourth-and-inches. "We thought we had the first down, but unfortunately, I guess twice, we didn't. By the way they spotted the ball, they made it look like I lost a yard."

Right tackle Winston Justice said: "We should have pushed them back more. It shouldn't have been close."

Center Jamaal Jackson seemed frustrated to have to answer questions about short-yardage shortcomings yet again, when, in his view, the line didn't fail this time.

"You didn't even have to look at the replay" to know McNabb got the first down, Jackson said.

But right from the beginning, you could tell this was not going to be a sharp, swarming win like last week's romp. The Cowboys were getting strong pressure on McNabb, and the Eagles weren't handling it with aplomb. First Birds series, a hurried third-and-5 pass bounced off Jeremy Maclin's hands, right to Dallas' Gerald Sensabaugh, and McNabb had been picked off for the first time since the season opener, at Carolina.

The pick gave Dallas the ball at the Birds' 37. The Cowboys needed seven plays to score, the key blow a 21-yard flanker screen to Kevin Ogletree on third-and-9 from the Eagles' 23. The Eagles used a funky defensive alignment that featured no down linemen. The Cowboys didn't seem too confused.

Incredibly, late in the first half, the same play set up the 'Boys' other points of the half, Ogletree scampering from the Eagles' 21 to their 4 on third-and-14. Down linemen were present this time, but the result was the same, Dallas setting up a wide corridor. Nick Folk eventually gave the Cowboys a 10-6 halftime advantage with a 22-yard field goal.

The Eagles got their first-half points on a pair of David Akers field goals, their power running game belatedly taking a little of the pass rush pressure off McNabb. The o-line was scrambled much of the first half, after the Cowboys' Jay Ratliff rolled up Jason Peters' ankle while sacking McNabb. Todd Herremans shifted out to left tackle, Nick Cole moved from right to left guard, and Stacy Andrews replaced Cole. Peters went for X-rays but returned at the 2-minute warning.

At halftime, both of the premier wideouts were without a catch - neither the Eagles' DeSean Jackson nor Cowboys rising star Miles Austin was on the scoresheet. McCoy had 45 yards on seven carries, subbing for Westbrook. Fullback Leonard Weaver had five carries for 23 yards. Both Romo and McNabb had been sacked three times, though on a number of snaps, Romo seemed to have more time to throw.

The Eagles came out much sharper for the second half. Ellis Hobbs' 96-yard kickoff return for a touchdown was negated by a Moise Fokou hold (he might be trying to set a record), but the Birds drove 77 yards in six plays and scored a go-ahead touchdown anyway. The capper was a scrambling 11-yard pass from McNabb to clutch tight end Brent Celek.

Dallas challenged whether McNabb was over the line of scrimmage when he released the pass. Astute Eagles fans who remembered the Eli Manning ruling against the Eagles from last season knew the challenge would fail. Manning, you might recall, seemed way over the line at first glance, but it turned out that the back of his back heel was on the line, and under the rules, that was enough. McNabb's back heel was squarely planted on the red line-of-scrimmage line on TV replays. Assuming the line was accurate, he wasn't over, and indeed, that turned out to be the ruling.

The Eagles didn't just take over and keep going, though. First they lost corner Asante Samuel temporarily when he took a Felix Jones knee to the head; the official word was a neck injury, the same affliction that later took sub Hobbs out of action. Then a slightly underthrown pass down the middle to Maclin was intercepted by corner Mike Jenkins, with Maclin kind of waving feebly at the ball, then grabbing Jenkins' facemask. The Eagles' defense had to work hard to hold Dallas to a game-tying 33-yard field goal, on the second snap of the fourth quarter.

"I was expecting a different throw than what he threw," Maclin said.

McNabb said he saw Maclin past the safety and put too much air under the ball.

The challenge-denial situation turned hard the other way when the Eagles objected to the spot on McNabb's sneak. Replays showed McNabb's progress, measured against the Eagles' logo painted on the middle of the field, just about had to be at least a few inches ahead of where he was spotted, which was an inch or two from a first down. But the replay official didn't see it that way, and Dallas got the ball. The Eagles, who might have considered challenging the spot on McCoy's third down try if they hadn't had another crack, were furious.

The killer came on the ensuing Cowboys possession, third-and-14 from the Eagles' 49, unbelievably enough, Austin all alone for his first catch of the night, against what seemed to be blown zone coverage. It was 20-13, Dallas, with 8:04 left. Reid said the Birds were fooled by a double move; Sheldon Brown seemed to be the prime victim.

The Eagles got another Akers field goal - a 52-yarder with 4:27 left, a great night for the kicker - but they couldn't stop the Cowboys from rolling to a couple first downs and running out the clock.

It was another game without a clutch fourth-quarter comeback from a team that doesn't seem to ever win that way anymore, another game that left you wondering about the Eagles' identity, and their prospects going forward.

Unoffically, the Birds have lost the last 12 times they've trailed in the fourth.

"It's tough to win when you get a couple calls where its tough on you, but we've won games in the fourth quarter," McNabb said. "I know that's something everybody's going to talk about. Have fun with it, I guess."

For more Eagles coverage and opinion, read the Daily News' Eagles blog, Eagletarian, at www.eagletarian.com.