"Mapping network printers..." on login takes a long time. When enabling logging for pnshell, pnshell is waiting at "ApplyNetworkPrinters".
Delete the users profile on the terminal server and recreate it.
If this does not help, it is possible to select which printers to map using the "Quest vWorkspace Universal Printer Client" in Control Panel on the client machine.
Select the "Auto-Create specific printers only" option and specify a few printers to test with.
If the users are getting their printers assigned via the vWorkspace console (Under Resources > Printers), try unassigning the printer from the user to see if they are then able to log in OK and attempt to isolate the printer which is causing the timeout.