All our workstations run Windows 7 Professional 64 bit. It started with one, then another, then another couple of machines having a problem accessing Word files locally and on the network. This doesn't happen on my machine though. Affected users get the error message 'There was a problem sending the command to the program'.

I've Googled for solutions, but none of the answers worked. They suggested deleting certain registry keys; unregistering and reregistering the program for DDE; resetting the way that the shell opens .docx programs etc. each to no avail.

As it affects local and network shares I believe the problem lies with the clients, and not the server, and I'm starting to suspect that there could have been a recent Windows Update which has caused this. I've tried comparing the updates on my working machine with an affected machine, but I can't immediately see any major differences.

Has anyone else recently encountered this problem? What are the best steps to take to further isolate what could be causing this?