Typical vista problems at zak.

Might I suggest getting Windows Vista Service Pack 2?

If that doesn't work, Start at full graphics and after arms lower the graphics down one notch, after the 1st body, lower them again one notch, and continue for the rest of the bodies. Make sure you're also in Windowed mode.

I've been on at least 5 zak runs since a little after this thread was posted, and the changing graphics thing works fine.

Windowed mode has absolutely nothing to do with it though.