I'm suddenly having the same problem. It started about two weeks ago here at work. We can't open files that are deep in the network. The pathlength is not so long, however, that we should be unable to open the files.

We can open these "unopenable" files if we move them to another folder "less deep" in the network or to i.e. the desktop, or we can open them with Open Office from the original location. There should not be any possibility of file incompatibility since no one here uses Office 2007 yet. Anyways, I made the original files less than ~6 weeks ago and the original locations, and they opened and saved fine at that time. Very strange.