I just found the source of a "Fatal Error...at xxxxx" that I had started getting whenever I tried to open a dwg file; perhaps it will help someone else try to troubleshoot these elusive problems.

I still use R14 sometimes and have it installed on a computer with Windows XP. The drive where the AutoCad program and data files live was compressed in XP and then the shutdown fatal errors started. I uncompressed the drive and folders, and the problem went away. this problem doesn't seem to affect Windows 2000 or 98 computer installations.