The Panthers (16-21-9) led Carolina 3-0 heading into the third period on Thursday, only to fall apart and lose 6-4.
"It's like something rotten in our stomachs," defenseman Mike Van Ryn said of the meltdown.
Florida outshot the Hurricanes 31-14 through the first two periods, and Carolina needed just 13 shots in the final period to hand the Panthers their fourth loss in five games.
"We should be able to hold a three-goal lead," Olli Jokinen said. "It's embarrassing."
Jokinen scored two goals on Thursday after recording a hat trick in the Panthers' 5-2 win over Pittsburgh on Wednesday.
Jokinen, who leads Florida with 21 goals and 48 points, has eight goals and nine assists in his last 12 games.
The Panthers captain has struggled against the Capitals (19-18-7) lately, though, failing to score a point in his last four games against them, and the team has suffered as a result.
Washington has won three straight games over Florida and has outscored the Panthers 9-3 in its two meetings this season.
Panthers goalie Alex Auld took the loss in both starts against the Capitals this season, and allowed five goals on Thursday.
Auld has been struggling lately in net, going just 1-3-2 with a 3.92 goals-against average since Dec. 9, while Ed Belfour is 5-1-2 with a 2.46 GAA since Dec. 16.
Although Florida has just one win in 2007, it has won three straight games, and four of its last five on home ice.
Washington, meanwhile, has lost a season-high four straight road games after opening a four-game road trip with a 5-4 defeat at Tampa Bay on Thursday.
The loss snapped a three-game win streak, but the Capitals continued to put pressure on its opponents' goal. Washington has scored 18 goals in its last four games, after netting just 10 in its previous five games - all losses.
"The fans want to see scoring. You had a lot of skill out there," Capitals coach Glen Hanlon said.
Alexander Semin scored two goals against the Lightning for his third multigoal game in his last four. He has seven goals and two assists in his last four games.
Alexander Ovechkin had two assists on Thursday, and has three goals and eight assists in his last five games.
Ovechkin, who was named to the Eastern Conference starting lineup on Tuesday for the All-Star game, had a goal and an assist in Washington's 4-1 win over Florida on Nov. 13. The 21-year-old star has four goals and six assists in 10 career games against the Panthers.
Olaf Kolzig made just 20 saves on Thursday, and is 0-3 with a 4.39 GAA on the road since Dec. 29.
Kolzig won both starts against the Panthers this season, making 78 saves in those games, snapping a six-game losing streak against Florida.