Ok this is an odd one, but is happening often enough its getting quite annoying.
I recently installed Windows 7 on my work computer (about 2 months ago) and every so often I lose access to network shares on our work network.
Its one server in particular - other shares are still working fine.
I have a number of folders mapped as a drive, and all of the ones on a particular file server have lost access. If I try to access the machine directly (\fileserver\d$) it doesn't work either with this message:
Windows cannot access \fileserver\d$. You do not have permission to access \fileserver\d$. Contact your network administrator to request access
Once I reboot the computer, access is restored like it should be. The computers are all on a domain and my user has administrator level access to the server in question.