Thanks for the hint. Unfortunately, I'm unable to select the option to disable spooling; whenever I change this option and hit Apply or OK, I get an error message about Windows not being able to save the settings. I can change everything else without problems.
A bit fishy, really.
However, after much experimenting I was able to solve the problem on my machine. It turned out that BitDefender Internet Security 2011 is the culprit: Disabling its "Active Virus Control" and IDS features (under Advanced Settings in Expert mode), or adding
splwow64 to the exception list, allows printing from 32-bit programs.
I should add that this is with only the default updates installed, i.e. without SP1 beta and the legacy printing fix.