I have a website that suddenly started to crash internet explorer.
The website loads and starts executing javascript but somewhere in there the machinery explodes. I
Stop using VML?
If you need stuff in IE that really can't be done by moving, scaling, cropping and replacing images, then consider using Flash, Silverlight or similar.
If your life depend on VML then read as much as possible about other peoples experience, that may ease the trial and error approach.