Cork Con took advantage of Shannon's slip up to move back to the summit in Division One. Five penalties from the boot of Munster-capped out-half Jeremy Manning helped Con to this win at the RDS.
Manning sent up a neat kick after only 90 seconds' play for winger Cronan Healy to collect and score in the right corner.
In the seventh-minute, Lansdowne's former Ireland U-20 prop Ruaidhri Murphy charged over for a try from 30 metres out.
However, Con fought back to lead 11-7 at half-time and Manning's boot did the rest.
Winless in their last five Division One games, Lansdowne came into this fixture looking to make amends for some poor recent performances, but they got off to an awful start when the New Zealand-born Manning orchestrated Con's first try.
Manning combined well throughout with his half-back partner Duncan Williams, who caused plenty of problems for Lansdowne around the fringes of rucks.
Lansdowne responded in style to that early concession when young prop Murphy took the ball on and managed to beat the cover defence to score a fine try, which Robbie Dolan converted for the lead.
Unfortunately, both Murphy and Con front rower Colm Murphy went off injured during the first half and those stoppages broke up the play, as did former Con captain Frank Cogan's yellow card in the 20th minute.
Playing with 14 men did not see to phase Con - it seemed to unify them. Penalties followed from Manning after 27 and 32 minutes - his second kick a beauty from close to the halfway line - as Brian Walsh's men moved 11-7 clear.
The second half saw the heavier Con pack gradually get on top and with Lansdowne's lineout coming unstuck, the Leesiders added to their lead.
Dolan did briefly make it 11-10, but successful kicks from Manning after 52, 59 and 71 minutes helped close out the game.
After being suffocated in their own half for much of that period, Lansdowne managed to gain some decent territory in the dying embers of this game and a Dolan penalty in the 79th minute notched a losing bonus point for the Dublin 4 outfit.
Scorers: Lansdowne: Try: Ruaidhri Murphy; Con: Robbie Dolan; Pens: Robbie Dolan 2
Cork Constitution: Try: Cronan Healy; Pens: Jeremy Manning 5
A converted try from captain Michael Hastings helped UCD record their eighth win in ten AIB League meetings with Galwegians at Belfield.
A swift counter-attack from the Students sent Hastings hurtling over the line early on in this dour encounter.
Killian Lett converted and also fired over a clinching penalty, five minutes from time, to seal the win and deny 'Wegians a losing bonus point. The wind and rain made play a lottery at times and the visitors disappointed against a lively UCD pack.
UCD: Try: Michael Hastings; Con: Killian Lett; Pen: Killian Lett
A try just after half-time from second row Frank McKenna saw in-form Garryowen edge out UL Bohemians at the UL Bowl.
McKenna muscled over off a close range drive, with full-back Conor Kilroy converting, to help the visitors into a 16-9 lead.
Played in wet and windy conditions, Garryowen led 9-6 at the break despite the best efforts of Bohs number 10 Fergal Lawlor.
The hosts did cross the whitewash through centre Colman Finn but Garryowen held firm for their fourth league win on the trot.
Scorers: UL Bohemians: Try: Colman Finn; Pens: Fergal Lawlor 3
Garryowen: Try: Frank McKenna; Con: Conor Kilroy; Pens: Conor Kilroy 2, Gerry Hurley 2
Greystones lost a match they should really have won at Templeville Road, as St Mary's College took the spoils.
'Stones had the better of possession and territory but a lack of firepower, and two late sin-binnings for hooker Alex O'Sullivan and flanker Fraser Clifford cost them dearly.
Mary's full-back Robert Gannon touched down early, after gathering a Matthew D'Arcy kick.
Three penalties from out-half James Power reduced the arrears for Greystones to 10-9 at half-time, but a late drop goal from his opposite number Frank Lynch saw Mary's triumph.
'Stones, who have slipped to bottom spot on foot of this defeat, will be kicking themselves as they had the winning of this game.
They did have their gripes with referee Paul Haycock, but they only have themselves to blame for missing out on back-to-back wins.
Mary's started like a steam train, scoring 10 points in the opening six minutes.
Prop Robert Sweeney made a burst forward and when the ball was recycled, scrum-half D'Arcy kicked through for Gannon to race up, gather the ball and finish.
Out-half Lynch converted and added a penalty for a sudden 10-0 buffer and the Dubliners looked set for a good day at the office.
However, with the rain beginning to fall and dropped passes blighting the home side's play, Greystones got themselves back in touch.
Power kicked two penalties and with his side establishing dominance in the scrum and lineout, a third successful kick followed to make it a one-point game just before half-time.
'Stones laid siege to the Mary's line in the second half, but try as they might, Mary's would not be moved.
The home side continued to cling on to their slender lead and even shunned a couple of penalty kicks close to the posts in favour of kicking for touch and keeping 'Stones pinned back in their 22.
They succeeded in frustrating the life out of last season's Division Two play-off champions, and Lynch angled over an injury-time drop goal to put the seal on his side's third win in four home games this term.
Scorers: St Mary's College: Try: Robert Gannon; Con: Frank Lynch; Pen: Frank Lynch; Drop: Frank Lynch
Greystones: Pens: James Power 3