David, I've had problems with Win2000 and SP2 when saving forms. Basically, the whole PC crashes, and not only do you lose the work you've just done, but the form itself becomes damaged. The error 'not a table' is displayed when you next try to view the form/compile the application.

I regularly backup my code, several times a day, to minimise the potential damaged caused. I've yet to find a solution to this problem.