winvista gpo log script odd behavior

Testing Environment: Virtual Server 2k5 R2 hosted on Win2k3 Ent x64 Ed. Testing Environment LAN: Local NAT bound to MS loopback adapter with WAN access via ICS
Virtual OS Instances:
Win2K Server: Virtual AD PDC. WinXP: Client Machine WinVista: Client Machine
GPO Log On Script: Language:VBS. Purpose: Map Three Network Drives (X,Y,Z) located on PDC
Problem: When logging onto the WinVista instance with an AD account that is a member of Either the local Admin Group or local Power Users group (test account is a member of one or the other never both) the VBS logon script fails to acctually mount the network shares. I have verified that the script is running by inserting a couple wscript.echo statements before and after the wscript.mapnetworkdrive statements, the wscript.echo's come up as expected but no network drives. If I remove the AD account from the local Admin or Power Users Group the drives map perfectly upon next log on. If I perform the exact same test on the XP instance (ie add the testing account to either Local Admin or Power Users) drives map perfectly in both cases.
Any Ideas