This is the likely cause of your error. Just because the driver does not
natively exist, does NOT mean the first course of action is to install the
manufacturers drivers, as this is the easiest way (next to making everyone an
admin) to de-stabilize your terminal server.
The preferred methods are via one of the following:
1. Manual User Defined Inf File Mapping of the unsupported printer to a
built-in compatible driver.
http://www.sessioncomputing.com/printing.htm
2. Via the Terminal Services Printer Redirection Wizard (automates creating
the file and registry settings that would be created manually in number 1).
3. Via Fallback Printer Driver in 2003 SP1 (an on the fly automation of the
printer mappings done in 1 and 2).
4. via 3rd party printing program like ThinPrint .Print RDP Engine,
triCerat Simplify Printing, or Provision Networks Print-IT. If you often
fight with printing problems, this is the best solution, as these will allow
you to print to virtually any printer w/o loading a new driver on the
terminal server each time.