Leinster missed the chance to take over at the top of the Pro12 table as they suffered a 12-6 loss away at Glasgow Warriors.
Rory Clegg - whose switch from French side Oyonnax was only confirmed on Thursday - was the hero for the home team, the fly-half starting his second spell with Glasgow by kicking four penalties at a sold-out Scotstoun Stadium.
Leinster's points all came from the boot of winger Isa Nacewa and, while they did manage to pick up a losing bonus point, they remain behind leaders Connacht in the standings.
In Cardiff, Munster's push for a top-four finish suffered a blow as they were beaten 37-28 by the Blues.
Rhys Patchell scored a fine solo try to secure a bonus point for the hosts, with the fly-half also kicking four conversions and two penalties to finish with a personal haul of 19 points.
Macauley Cook, Matthew Rees and Garyn Smith also touched down for the Blues, who led 10-8 at the interval and were able to keep their noses in front throughout an action-packed second half at Cardiff Arms Park.
Winger Darren Sweetnam's try saw the visitors race into an 8-0 lead inside seven minutes, yet they were unable to build on their fast start.
They remained in touch after the break thanks to tries from forwards Mike Sherry and Jack O'Donoghue, with the latter's effort cutting the gap to six points in the final minute.
Yet Munster, who saw Ian Keatley kick one conversion and two penalties, failed to even pick up a losing bonus point due to a last-gasp penalty from Blues replacement Jarrod Evans.