Rangers undid a lot of the good work of recent weeks with a sloppy performance as they dropped two points against a determined Dundee United.
It looked as though Nacho Novo's second-half goal would be enough to see the home side through. However, in the last minute of normal time Barry Robson, a former Rangers player, equalised with a free-kick which stunned Ibrox.
The share of the points could prove a severe setback to Rangers' league ambitions as they are now seven points adrift of Celtic.
Peter Lovenkrands was named on the teamsheet but was withdrawn after being sick in the warm up, with Novo replacing the Dane.
Rangers began with plenty of gusto and within two minutes had hit the woodwork. Novo's deep cross was headed back across goal by Dado Prso but, with the keeper stranded, his effort came back off the post.
Prso was winning his share of the balls in the air but Shota Arveladze was slow to read his flicks. A Novo shot was then easily gathered by Paul Jarvie as Rangers early promise faded.
In a swift break Zurab Khizanishvili dispossessed Robson but his final pass found Prso offside, which was a common fault of the Rangers player.
Gregory Vignal had a couple of long-range efforts which failed to trouble Jarvie as Rangers became more and more ragged.
The power of Fernando Ricksen's free-kick nearly surprised Jarvie after After Arveladze was fouled on the edge of the box. From another free-kick Prso nodded down at the back post but no-one reacted quickly enough and Jarvie gathered.
The United keeper required two attempts to keep out Novo's swerving shot before Prso hooked the rebound wide.
At the start of the second half Marvin Andrews headed clear two dangerous free-kicks from Robson before Steven Thompson came on for the ineffective Arveladze. Ricksen was off target with a long-range effort as Rangers struggled to find any rhythm.
Prso cleverly teed up a chance for Ricksen only to see his shot easily saved by Jarvie.
Rangers finally took the lead after United conceded possession. Vignal's pass found Novo and, with Prso's run dragging Chris Innes away, Novo lashed his shot high into the top corner before being booked for his celebration.
Thompson went close minutes later with a glancing header from Chris Burke's cross.
Just as it seemed Rangers would hang on, United equalised.
Robson's first free-kick was blocked by the Ibrox defensive wall bur Prso fouled substitute Karim Kerkar in the resulting melee. This time Robson made no mistake, with a curling effort into the top corner leaving Stefan Klos helpless.
In injury time Derek McInnes was booked for advancing too quickly on Ricksen's free-kick before Bob Malcolm shot over as Rangers desperately tried to regain the lead.