PSG blew their chance to lead the French Ligue 1 after going down at Sedan while Bordeaux's visit to Nantes finished goalless.
High-flying Paris Saint-Germain suffered a shock 3-1 defeat at Sedan but the Parisians stay second behind Auxerre.
They were drubbed by a team who have taken up residency in the bottom half this season, with Ludovic Asuar scoring twice for the home side.
Stephane Noro put Sedan ahead early on, Frederic Dehu equalised for PSG before half-time and then Asuar struck twice in the second half.
Noro's goal came after just nine minutes and was a spectacular strike.
Coming from a situation that did not appear too alarming for PSG, Noro looked up 25 yards from goal and decided his best option was a shot.
It was the right choice, with the ball arrowing into the top right corner of the PSG goal.
PSG restored parity in the 35th minute to give themselves hope of getting the point which would have taken them top on goal difference.
Ronaldinho swung a free-kick into the penalty area and Frederic Dehu was in the right place to head in.
Sedan went back into the lead after 51 minutes with Asuar proving himself lethal from 15 yards.
He received a pass from Cedric Mionnet in the centre of the penalty area and calmly sidefooted the ball past Lionel Letizi who was left flat-footed.
PSG replaced Lionel Potillon with the more attack-minded Andre Luiz, but Luis Fernandez's tactical switch failed to produce the outcome he will have hoped for.
And the Parisians fell further behind in the 69th minute when Mionnet again picked out Asuar and - from slightly further out than his first strike - he again placed the ball out of the reach of Letizi and precisely into the goal.
There was no way back from there, with the most notable event of the last half hour being the way Ronaldinho reacted to being substituted.
The Brazilian World Cup winner was hauled off in the 71st minute after a largely ineffective performance, and ignored coach Fernandez as he headed straight for the dressing rooms.
Fernandez should be able to turn around his team's fortunes providing his star man stays, but if Ronaldinho decides he has had enough of life in France then PSG might struggle to keep up with the pace.
Nantes and Bordeaux both finished dissatisfied as they fought out a scoreless draw and failed to kick-start their misfiring championship campaigns.
The game was card heavy, with referee Bruno Derrien handing out five to the visiting Bordeaux side and two to Nantes.
Both teams were among the title favourites before the season but are in urgent need of points to help them up from their current positions in the bottom half.
They will certainly have to do better than their efforts here, which lacked invention and penetration.
Bordeaux's Portuguese striker Pauleta was a major culprit when it came to poor finishing, spooning a shot horribly high and wide after 27 minutes and moments later contriving to fire over from just four yards out.
Nantes created a good chance in the 64th minute, with Gregory Pujol, Mathieu Berson and Stephane Ziani combining to set up Marama Vahirua in the centre, but his well placed header was saved by Ulrich Rame.
Neither side seemed eager to make the changes necessary to really chase a victory and a goalless draw was the inevitable result.