Ulster had to settle for a share of the spoils in a 29-29 draw against Treviso in the RaboDirect Pro 12, which means Mark Anscombe's men have won just one of their last four games.
A hat-trick of tries from flanker Dean Budd, a single score from Robert Barbieri and a penalty and three conversions from Alberto Di Bernardo got Treviso the draw, which also saw them register a try bonus only five days after putting Munster to the sword in Italy.
Though they avoided defeat, thanks to tries from Andrew Trimble and Stuart Olding and 19 valuable points from Paddy Jackson, Ulster's slump in form has done considerable damage in their push for a home semi-final.
Scarlets climbed back into the places but that was after securing an unconvincing 14-13 victory over struggling Edinburgh at Parc y Scarlets.
Scarlets surrendered an early 8-0 lead before replacement fly-half Owen Williams kicked a penalty 13 minutes from time which was enough to condemn Edinburgh to an 11 straight defeat in all competitions.
Leinster consolidated their place in the play-off zone with a bonus point 26-19 win against struggling Newport Gwent Dragons.
The European champions ran in four tries, two each for Sean Cronin and Dave Kearney, at Rodney Parade to record their eighth victory on the spin.
Glasgow maintained their drive for a top-two finish and a home tie in the semi-finals after coming from behind to beat Cardiff 29-13.
It was their seventh win in a row and fifth successive five-pointer to claim a new league record surpassing the one set by the Dragons in 2004. The bonus-point win puts them equal with Ulster on 61 points at the top of the league and with the better points difference they become the leaders.
Elsewhere, Dan Parks kicked a late drop goal and penalty to guide Connacht to a battling 23-19 win over Zebre at the Sportsground.