Leinster's winning run came to an agonising end on Friday as they were beaten by a late Mark Bennett try in a 29-24 Pro14 defeat to Edinburgh.
Last season's semi-finalists had not lost in any competition since their last trip to Scotland in November, racking up nine consecutive wins since that defeat to Glasgow Warriors.
The Irish province led 19-17 at half-time after tries from Max Deegan, Scott Fardy and Barry Daly, whose second try of the match sent Leinster 24-22 in front with 16 minutes left to play.
However, Bennett - on the end of a Jaco van der Walt chip that was touched down by Glenn Bryce - crossed with two minutes remaining and Sam Hidalgo-Clyne converted to put the match beyond Leinster, who go level on points with Conference B leaders the Scarlets thanks to their two bonus points.
Ulster are now eight points adrift of the top two after they subjected the sorry Southern Kings to another thumping defeat at the Kingspan Stadium - a match that saw Joy Neville become the first woman to referee a Pro14 fixture.
The hosts racked up nine tries in a 59-10 demolition, although the seventh came at a cost, with Rob Lyttle left writhing in agony with a hamstring injury after running the length of the pitch.
A blistering run by Rob Lyttle to make it try number seven for @UlsterRugby, but he's paid a heavy price with what looks to be a hamstring injury!-- PRO14 RUGBY (@PRO14Official) February 9, 2018
Watch the closing stages LIVE BBC Sport NI & BBC ALBA#ULSvKIN#GUINNESSPRO14pic.twitter.com/dYckFOLMb8
The Dragons missed out on a first Pro14 win since September as they were held to a 15-15 draw by Conference A leaders Glasgow Warriors, while Connacht beat the Ospreys 26-15 following back-to-back defeats.