Delays opening Office 2010 files protected by Nonstop Backup over the network

I use Acronis Nonstop Backup on my file server.

If I try to open the protected files on Windows 7 clients I experience the following problem:

* Opening of Microsoft Office 2010 files takes 1 minute and more.

* If I open the same files on the fileserver I do not experience any delay.

* If I switch off the nonstop backup service I can open the files on the clients in lightening speed.

* Other files (e.g. pdf) are not affected at all.

Any ideas?

Regards

Hanns