Problem opening files that are scheduled for backup

[k2itmgr]

Ok, here's the situation.

Windows 2008 server is hosting a fileserver.
Symantec Backup exec 12.5

Other computers connect to the fileserver through a workgroup.  I've basically given everybody full control over the shared folder, as it's a closed connection and only those who need access have drops to the server.  The shared folder is scheduled to be backed up every night.  However, when users try to open the files through the server, the files can't be opened.  They can be copied to the local machines and opened, but that isn't suitable to our needs.  I can't even open the files as the server administrator on the server machine itself. 

Now, when I copy the files from the standard location to another location on the server, say the desktop, the files open fine.  Also of note, I've created another shared folder and copied the files to that share and am able to open the files without difficulty.  This share is not scheduled to be backed up.

It leaves me to believe that the problem is with the backup exec system.

Any advice?

Thanks.

[Ben_L_]

Is this happening during the backup or does it happen outside of the backup window?

If you create a new file and place it on the share, are you able to open it from the share?

Are you backing up the data via the remote agent or just via the share?

[k2itmgr]

Right, this is happening outside of the scheduled backup time. 

I'm backing up the data locally onto a NAS.

I'm not sure of the 2nd question yet, but will look into it in a few moments.

[Ben_L_]

What happens if you create a new file on your desktop then copy it over to the share that is being backed up, can you open the file?

If you wait till after the next backup is run are you still able to open the file or not?