Hearts conceded three goals at home for the second week running as they lost 3-2 to Inverness to see their top-six ambitions dented.
The Tynecastle defeat leaves last season's Scottish Cup winners stuck in 10th place, seven points from the upper half of the Premier League. Terry Butcher's team, however, were able to regain second spot in the standings as they recorded just their second win in eight games.
The home side were undone by a Gary Warren double which came either side of Billy McKay's 22nd strike of the season. Yet Hearts had twice equalised through Jason Holt and a deflected Andy Webster strike - but both times handed the initiative back to their Highland visitors within minutes.
Aberdeen were unable to make their chances count as Kilmarnock battled back to earn a 1-1 draw at Rugby Park.
Rory Fallon's brilliant volley gave the Pittodrie side the lead they deserved before Paul Heffernan got Kilmarnock back on terms five minutes before half-time.
Ross County stretched their unbeaten run in 2013 to eight games with a 3-0 win against Motherwell at Global Energy Stadium.
After a slow start County went on to dominate the match with Ivan Sproule scoring his firth goal in as many starts to give County the lead in the 11 minutes from the break. Second half goals from Richard Brittain and Iain Vigurs completed a fine second-half display from the home side.
Rowan Vine's scrambled goal consolidated St Johnstone's position in the top half of the table by delivering a 1-0 victory over St Mirren.
Vine shot home from close range early in the second half after Murray Davidson had bundled the ball goalwards following Mehdi Abeid's corner in a goal that followed a similarly scrappy first 45 minutes on a bumpy McDiarmid Park pitch.