Wayne Ellington's would-be game-winner fell through the basket just after the final buzzer sounded, as Carolina (22-4, 8-3 ACC) struggled to find its offense with the game on the line.
Ty Lawson took a missed free throw and drove the length of the court with seven seconds showing on the clock in the overtime, but his shot attempt was blocked by Deron Washington. The ball caromed among players before Ellington grabbed it at the top of the key. But there was insufficient time for his double-clutched three-point prayer to be answered.
"We were supposed to run a play, but they came and doubled so that messed everything up," Lawson said describing the Tar Heels' last possession. "I couldn't find anybody open, so I tried to get a shot off, but they blocked it in the lane. They clogged the lane. I think they knew what we were going to do."
UNC made just one field goal in the extra period, and Tyler Hansbrough missed the first of two key foul shots which would have enabled Carolina to tie the score with 14 seconds remaining.
"This game's very frustrating, especially at home against a team that's already beaten you," said Hansbrough, who scored a team-high 22 points. "We wanted to come in here and get a big win since they beat us like they did at their place, but we just didn't make the big plays that we needed. They're physical and they run a lot, so they're tough."
Despite leads of seven points on three separate occasions in the second half, the Tar Heels were unable to extend their lead primarily due to a 0-for-8 three-point shooting performance after halftime. They were 3-of-17 from beyond the arc for the game.
Carolina had a chance to win the game in regulation with the score tied at 73 apiece, but a Lawson isolation play yielded only a long-range three attempt by the freshman which bounced off the back of the rim.
Lawson finished with 13 points, and Ellington added 14.
"I felt very good at the end of regulation that we were going to get a better shot," said Roy Williams, who took the loss hard and blamed himself in the post-game press conference.
"That was the worst coaching job that I've ever done," he said. "My job is to have kids know what to do. It was bad coaching and the kids deserve more than that."
Zabian Dowdell led all scorers with 33 points – the most by a UNC opponent since Duke's J.J. Redick went for 35 last season – and Washington pulled down 14 rebounds to lead the Hokies (18-7, 8-3) to their first win in Chapel Hill since Feb. 12, 1966.
In the two games versus the Tar Heels this season, Dowdell converted 28-of-34 free throws.
"That was as big of a team win as I've ever been associated with," VT coach Seth Greenberg said. "That's a special group we played against, and we were just fortunate enough to get another stop. There is such a thin line between winning and losing."
Carolina has now dropped six consecutive overtime contests, with four coming at home.
The Tar Heels slipped into a three-way tie for second-place in the ACC with Virginia Tech and Virginia. They travel to conference leader Boston College (18-6, 9-2) on Saturday for a 9 p.m. tip-off, with the Eagles still to host Duke on Wednesday.
"We need to wake up," Marcus Ginyard said. "These last two days of practice were absolutely terrible. It just showed tonight. We need to get our mind right for practice and we've got another
tough game on the road. We have to learn from this game and we really have to wake up."