My issue appears similar to the one in this unanswered question but I didn't want to hijack that thread since it seems it might have gone a little stale.
Issue: When a user attempts to open an excel document they get the following two errors.
"Could not open 'http://<filelocation>'."
Upon hitting okay:
Microsoft Excel cannot open the file 'http://<filelocation>' There are several possible reasons:
* The file name or path does not exist.
* The file is being used by another program.
* The workbook you are trying to save has the same name as a currently open workbook.
Variables:
- So far this has only happened on systems running Windows XP with Sharepoint 2010
- Once it happens that URL seems to be completely locked out for that user. Rename the document and it works fine. Change the name back and it will be broken again.
- I've cleared all history and reset IE 8
- Not all users with the same configuration experience the problem with the same documents.