We have a network drive that stores our files but we frequently have in progress work that is created on the Macs and then pulled up on our Windows 7 machine for different reasons. That is when the problem rears its head. The Windows 7 machine seems to lose all local computer access even other Windows machines. The machine in question was also recently upgraded with a new MB and CPU so I doubt it is a hardware issue.
It seems to happen randomly, but generally during an 8 hour day it will happen 4-6 times.