The Orioles were in overdrive tonight, leading, 3-2, and cruising toward their ninth victory in their last 10 games when one of the soundest cogs in their well-oiled machine broke loose.

Cal Ripken Jr., the rookie who is leading American League third basemen in fielding percentage, flagged down a hard grounder but threw high to first base with two out in the eighth inning. The Milwaukee Brewers had a reprieve and a man on base. They scored twice that inning and took the lead, and in the ninth they scored two more runs for a 6-3 victory before 18,420 at Memorial Stadium.

It was Ripken's first error in 45 games since April 23 and it pulled the rug from under Mike Flanagan's fine pitching performance. Flanagan had been breezing along since the first inning, when he gave up two runs on Robin Yount's eighth homer this year.

The Orioles closed to 2-1 on Eddie Murray's eighth homer leading off the second, and they took a 3-2 lead on Dan Ford's bases loaded single up the middle in the third.

After that first inning, Flanagan allowed only three singles until the eighth when, with two out, Mark Brouhard sent a hard grounder down the third base line.

Ripken made a backhand stab to stop the ball, then grabbed it with his bare hand as it popped out of his glove. "It was a tough play 'til I caught it," said a sheepish Ripken. "But then it became routine."

He took a hop-step and threw across the diamond. That would have ended the inning except that the ball sailed and by the time it reached first base Murray was leaping for it.

Murray tipped the ball and it went by him for the throwing error, Brouhard holding at first.

Paul Molitor followed with a clean single to center and Manager Earl Weaver made a visit to the mound. "I told Flanny he was in through (Cecil) Cooper," said Weaver, meaning the pitcher had two more batters to prove he still had his stuff.

But Yount, the next batter, made it 4-3 Milwaukee as he batted in his third and fourth runs of the night with a triple off the wall in the right-field corner.

Gorman Thomas chased Flanagan and made it 5-3 when he led off the ninth with a home run deep over the 360-foot mark in left field. Reliever Tippy Martinez lasted only two batters, giving up a walk and a single, and Tim Stoddard was called on to shut down the Brewers. He did, after a fashion, allowing one more run on pinch hitter Marshall Edwards' sacrifice fly.

The Orioles did not mount a threat in the ninth, as reliever Jim Slaton retired them in order. The victory went to starter Bob McClure (4-2), who bears the singular distinction of havng had Yount hit a home run in every one of his last five starts.

Flanagan (5-5) took the loss, his first in his last four starts. It was the first time in his last four starts that he had not pitched a complete game, and afterward he was disconsolate.

"Did you feel good out there?" someone asked.

"Oh yeah," he said sarcastically. "I had a great time."

Neither did the fielders, who were battling nubbly grounders after days of rain.

Shortstop Yount bobbled two consecutive ground balls in the sixth, salvaging one for the out but allowing Benny Ayala to reach base on the second. And Milwaukee center fielder Thomas let Ford's routine single bounce out of his glove for one of the Oriole runs in the third.

"The rain beating down on the tarp made the ground hard," Ripken explained.

Weaver concurred. "Evidently the field is fast and a little bumpy," the manager said. "Pat (groundskeeper Pat Santarone) hasn't had a chance to roll it out and make it smooth with all the rain."

Weaver defended his decision to leave Flanagan in to face Yount with two men on in the eighth.

"I didn't think Yount could put them ahead," he said. "Flanagan had held these guys so well. I figured maybe he gives up one run, but then he can get (the left-handed hitting) Cooper out. So we have a new (tied) ball game going into the ninth."

But, said Weaver, if he had it to do over again he'd bring in Stoddard to pitch to Yount.

"These are the ones," said the manager, "that keep you up all night because you never know what Stoddard would have done. It'd be nice if you could just get them all out there again so I could pitch Stoddard to Yount, just to know what would have happened.

"Then at least you could sleep."

Yankees 5, Red Sox 4