I recently submitted a ticket to Digital Services about the following issue:
Occasionally when a patron starts a PC Reservation session on the Windows 7 machines, the REFBW and REFCOLOR printers aren't showing up at all. It's as if they were never installed. When the patron goes to print something, their only option in the drop-down printer selection menu is the Microsoft XPS Document Writer.
As soon as you reboot the computer the printers will show up, but there's no way to print without ending the session and starting over.
If you encounter this problem, encourage the patrons to save their work to an external source (email, flash drive, etc.) and either switch computers or reboot their machine.