Wow... Groovey...

I've just checked the MS Knowledge base and you can have data loss, silent design changes to orms, reports, macros, modules, or commandbars, may be discarded without warning. Check out article Q237938 for more details.

But I have heard of other problems as well, although this was a couple of years ago with Access 95 which have probably been cleaned up by now. Or at least, I'd hope so!