Fairly new issue, and formatting the machine didn't help! (regularly scheduled format, didn't do it just for this).

When I try to open an XLS (Office 2003 / WinXP x64) thru the network, it appears to be trying to install something for a brief moment, then pops up with "Could not open 'http://Viridel/FileShare/yadda/yadda/yadda.xls' [OK]

Then when hitting [OK];

Cannot access the file 'http://(as above)' There are several possible reasons:
- The file name or path does not exist (yes it does, I can open other files on that same path, and if I copy the file locally, it opens perfectly)
- The file is being used by another program (no, it isn't, and even if it was, Excel would just open a Copy with a Save As option)
The workbook you are trying to save has the same name as a currently open workbook (nothing is open, so strike three)

I'm sure the issue lies with the fact that it's trying to open the file via HTTP, as that is what jumps out as being illogical in the error message.

For Word, I get the exact same error, then the document opens just fine (in DOC format) when I hit OK.