Comment 11 for bug 252079

the problem continues and I have not been able to fix it using any of the suggested solutions..

editing your profile's prefs.js files is the same as twiddling with about:config but you can search and replace and make the job less painful..
If you wait long enough (say 5-10 minutes) the prompt screen gets completed but the print option is greyed out.
Choosing anything else other than closing this window then causes the hang/lock/whatever.
At least you can return to the web page, close FF gracefully or continue [without printing]

in any case deleting print stuff from prefs.js/about:config never worked for me:
A cups restarts used to work but makes no difference now.
this is 3.05 & 3.06 on opensuse 64 and I think it could have something to do with no kde printing in FF3