When you open a file from sharepoint (I dont know if this only applies to office documents) and the application crashes (not Sharepoint), when you re-open the document from sharepoint you will get an error
FileName is locked for editing by ‘another user’.
Dont waste time looking for any temp files to delete just wait 10 Mins and reopen the document again from sharepoint it should of cleared the lock again.
http://support.microsoft.com/kb/899709/en-us
I know its not a big thing to blog but I thought I would anyway.
Update
I have written some other posts which may also fix the problem or give you some help, they areĀ
http://stephenmuller.com/2008/08/11/file-locked-by-another-using-moss-user-pt-2/
and