A document left open for several days and saved frequently will generate a
huge slew of temporary files (one for each save), and this alone might cause
the problem.
I don't believe the cause of these temp files is actually documented
anywhere. They are of the type ~$wrlxxx.tmp, which the KB
(
http://support.microsoft.com/?kbid=211632) says are associated with the
Clipboard, so perhaps they are not generated unless you have copied
something, but I can attest that, if you have "Automatically create backup
copy" enabled, in at least some instances the first save (Save As) will
create the file, the second save will result in a *.wbk file, and every
subsequent save will result in an additional ~$wrlxxx.tmp file. You can
actually open these files, and they are previous versions of the document.
They are all deleted when you close the document (or should be; there have
been some situations where they are not, and that causes a further problem).
The KB article does include this, which might explain the files:
"Text Pasted Between Files (Same Directory as Source File):
"When Word copies and pastes between documents, it may create a temporary
file in the same directory as the source file. This is especially true if
the source file is saved or closed. The temporary file represents the
information that was referenced by the Clipboard prior to saving the file.
Word creates this temporary file by renaming the old copy of the file to a
temporary file name."
Another problem with leaving a document open for extended periods is the
accumulation of the Undo stack. Moral to the story is to periodically close
and reopen the file.
