Can't open an Excel file from a shared drive

A user has tried to open an excel file from a shared drive to enter some data and he is now getting a message saying access denied, contact Admin. I have checked the permissions and he has full access, nothing has changed there.

I found that if the file is renamed, he can open it but when it is changed back to the original name, he gets the problem again. Basically, he cannot open the file under the name anymore.

Any help would be grateful because I have search everywhere and cant find a solution.

Maybe somewhat opened that file as read-only and it was cached? Tried restarting that particular PC?

edit: Hmm, can't open at all, right? Try restarting nevertheless

Check the PC that has the file for sessions and open files (computer management - Shared folders) and see if the user has an open connection, disconnect/close then try again

Yea, I've checked all that and its fine.

What I tried doing was.
Opening the file as a different user,
Changing the name of the file to something else and then save the file.
Delete the original file.
Then i have gone back to the user who couldn't open the file and got him to open the newly named file, which he was able to.
I then asked him to save the file with the original name, which he was able to do.
Then when he tries to open that file after renaming it, it comes up with the same issue.

Its as if its to do with the name of the file.

What security software are you using? Check its settings.

We use Sophos which has not changed and the permissions on the file and folder on our server which is 2008, are all set up correctly.

He can actually open the file once he has signed into a different computer, just the one he normal uses, when logged onto his account, just does not like the name of the file. We have tested it with a different user logging into his computer and they can access the file.

Does Microsoft Office store cache files somewhere on Windows 7 and if so, where can i find them?

Maybe the file was somewhat blacklisted by Sophos? Just guessing here to be honest.