I have just installed a new network with a SBS 2008 Standard server from Dell and 5 client PCs all running Vista Business SP2. I have Kaspersky Enterprise Space Security running on the server and deployed to the clients with the Kasperksy firewall turned off and the Windows Firewall enabled. After pressing Ctrl + Alt + Del and typing the user password two of the PCs will hang with the spinning wheel and "Welcome" on the screen and will stay that way. If I disconnect the network cable they will log in after a short delay. All the other PCs on the network have no issues. I have even uninstalled the Kaspersky from the affected PCs to see if it was the culprit but the behavior remained. I have looked into some articles that point to the WebClient service and another in relation to mapped drives (which they have). But nothing has worked so far. Any ideas?

Found the issue. The user profiles had become corrupt somehow. I backed up the user data in the profile and deleted it. Logged in again and let it make a new profile. Everything working fine.