I've been using Vista since beta 2 but I haven't had my network printer installed up to now.
Everytime I tried to install network printer I get the message saying: "Windows cannot connect to the printer. The specified print monitor is unknown." with the following screen.
I finally found solution on this here and here.
Simply said if you're in same situation then you must turn on UAC. Yes, you need UAC in order to install network printer. Once installed you can turn it off again.
Here was some intersting suggestion from javmirin:
In Vista PC's go to "Control Panel" - "Printers" - "Add printer".
Believe or not, click "Add a local printer" (I know you want to add a network printer but that way it doesn't work).
Click "Create a new port" - "Local Port" - "Next"
In the next box you have to enter a port name like this:
\\PC name\Printer name
where "PC name" is the network name of the XP PC where you have the printer and "Printer name" the network name of that printer. Be careful with this names. Check in your XP PC "Control Panel" - "Printers and faxes" - "your printer" - right click - "share" - "share resources name"
(sorry I'm translating from Spanish and not sure these are the exact terms).