Outlook 2010 Not Allowing Links To Files On Internal Network

I'm the net admin for a small network. One of my users has a problem that has just started today, apparently. When emailed a link to a file on the internal network, from another user on this same network, clicking on the link simply gives an error about it not being allowed. (This operation has been cancelled due to restrictions in effect on this computer. contact your system administrator.)

All users are admins on their own local boxes. This user could perform this function prior to today. There is no problem with the structure of the link, nor with security for the file in question. (I first verified that the user has access to the file, and he does, he can navigate via Windows Explorer to the location, open the file, even has write access to that location)

Even when creating an email, and not using a masked link, but a full UNC path, the 'Crtl click' to go to the location results in the same error.

I tried removing spaces from the file name, same error. I tried typing out a link to a share (not a file), one that has no spaces and I know he has access to, same error.

This represents a significant problem. My users need to be able to send links to internal locations and files, and not attachments (for multiple reasons).