Subsurf Problem

Yesterday, Blender 2.45 started crashing every time I try to add Subsurf to an object.
I have two versions of Blender on my computer: 2.45 and SVN. I tried Subsurfing something in the SVN version and the same thing happened.

Any clues as to what’s causing it? Should I re-install it?

I’m not sure if it’s related but around the same time I had tried compiling a plugin using plugin.def in the “plugins/include” file. Could that have messed something up?