I don't think this is anything to do with your security software.
I have Firefox and use McAfee security software and I do not get the option to print from a right click. I do get the option to print from a right click using IE8 though. In fact I get about 25 right click options with IE8 and about 10 with Firefox.
Until I read your thread I had never considered right clicking to print so cannot say whether or not Firefox has ever had that facility.
Looks like IE8 is better than Firefox in at least one aspect;-)