Since I upgraded from OSX 10.5.1 to 10.5.2 I haven't been able to use my shared printer on on my Windows server. Every job I submit gives me an error saying On Hold (Authentication Required).

There's no way that I could submit the printjob to the server from my Mac.

It seems that there is a bug in the authentication mechanism on OSX 10.5.2. If you add a (network) printer by using the System Preferences, you get to browse to find the actual printer.