It was desperately disappointing for the Dragons who dominated the second half but were made to pay a heavy price for failing to make the most of their chances. Ceri Sweeney, Michael Owen and Martyn Thomas all went close as the home team did everything but cross the try line.
Rhodri Gomer-Davies also made a hat-full of clear breaks but chance after chance went begging and the Dragons were always at risk of a sucker punch at 11-6. That came after the end of normal time with Connacht's first attack of the second half. Dunne kicked the Irish up-field and O'Connor squeezed over from the resulting lineout.
The losing bonus point leaves the Dragons five points behind the Ospreys in the hunt for Wales's third automatic place for Heineken Cup qualification. But that is little consolation for the Dragons after Owen and Sweeney opened an early 8-0 lead.
Paul Turner made five changes to the team that went down to Glasgow last time out and it was not long before they made their mark. Fit again fly half Sweeney kicked the opening points of the game after just four minutes before his break lead to the first try.
Sweeney was denied in the corner by fullback Gavin Duffy. But Connacht made a hash of the resulting line-out and Wales star Owen was gifted the easiest nine tries for the region.
Despite their lowly position in the Magners League, Connacht have been no pushovers for any side this season and clawed their way back into contention. Kiwi outside half Troy Nathan booted two penalties after David Gannon's try was ruled out following Duffy's forward pass.
Nathan missed the chance to put the Irish team ahead with a third penalty on 35 minutes. Instead, opposite number Sweeney hit the target again to open an 11-6 half-time lead for the Dragons.
They dominated the second half as the Dragons' backs tore strips into Connacht but the scoring pass eluded them.
Owen thought he had scored a second try but referee Neil Paterson ruled he had grounded the ball short of the line. In the end, the Dragons would pay for missing their chances.
Click Here for a Statistical Match Report from the Dragons v Connacht Magners League clash