but i had the same problem with my ibanez...
on the backside of the guitar, there should be a part where you can open it up and check the electrics.. there are two screws holding that keep the tremalo down... there are springs there for the wammy bar..
o ya and if you dont have a wammy bar, forget about this and stop reading now.. but if this sounds like you then...
loosen the strings to the point where you have dropped them almost to the edge.. then tighten the screws that keep the springs in place... dont break a string..
tighten the screws to where the almost touch the body of the guitar.. then, tighten your strings slowly and see if your bridge starts to raise up again..
if it does, you need to get more springs for the tremalo,
if not, then just re-tune your guitar, and jam...
p.s. you might need to restring, for the e B or G string might snap while retuning.