What version of AI and what type of document? How many objects? What styles/ appearances? This behavior seems to be caused by lack of resources, which can happen if you use complex blending operations, shape brushes etc.. Also if your stuff is not neatly organized into layers, things can get awfully slow. Does it do the same in isolation mode, btw.?
To be more specific then Mylenium this might mean not enough room on your scratch disk, font cache and perhaps other cache problems, a plug in
a new install of an application or haxie or perhaps or perhaps your disk might need to optimized if you only have one disk. You can try disk Warrior.
ok, thanks for the responses guys! I seem to have resolved the issue... I repaired the disk permissions and it seemed to do the trick!
I knew it!