Is Virus interfering with network?

I've added a laptop I brought from home to my two station wireless network at my office. This new station can be seen by the existing stations, but file access between the old and this new station is blocked. I've unistalled Zone Alarm thinking my firewall was to blame but still have the problem. File sharing settings are correct. I'm suspecting a virus - though I've run several of the more commone virus checkers and still have the problem. Any ideas?