Rick,
This a function of FM's autosave utility. If this is enabled, then when the time comes to save, FM copies the current file to filename.auto.fm.xxx (where xxx is a random hex value between 000-FFF), then deletes the prior auto-saved file if succcesful and finally renames the .xxx to the .auto.fm file. This three-step is to avoid corruption.
However, sometimes if there is network congestion, greedy/aggressive virus scanning or you're low on disk space or permissions/policies/ownership aren't properly set (especially under Win7 even when you have admin rights), then the temp file can't be renamed to the proper name and FM complains with the "odd suffix" mesage and leaves the .xxx version as is.
This issue is totally system dependent and something is interfering with FM's ability to rename at a low level.
AFAIK, this behaviour has been around FM from at least the first Windows version back in '92
See also this old thread: http://forums.adobe.com/thread/316082?tstart=0.