Internet Access using corporate network

We are having issues with computers running Vista Home Premium connecting to a wireless access point in our office which uses our corporate T1 line (and workgroup). Our server is running Windows 2000 SBS. We are getting a message that the network server is blocking access, but we don’t understand why that is the case, when the wireless router doesn’t technically use the server for access. We were also told that Vista Home Premium could adversely affect the network if we allowed access. Any thoughts or experience with this issue?