DGN files getting corrupt/reverting to blank

In the last one month, this has happened about 5 times.

User would open a DGN file, which was previously worked on, and the file would be completely empty, like it's a new file.

Since the phenomena is rare, and apparently there is no pattern to it, it is causing headaches for me.

Our network is mostly Windows 7 professional computers with some Windows 8 computers, all patched and updated.  Server is server 2008 running on ESXi.

4 out of 5 times this problem has happened with remote users, working off of the VPN.


Has anyone run into a similar situation before or has any insights?  Any help would be appreciated.  Thanks.