mozilla 1.6 and FCKeditor 2.2. Demo is working well with IE. The only sample working on Mozilla is the one with frameset. You 're right it maybe a setting problem but evrything is enable....
Although Mozilla 1.6 is quite old (you really should upgrade as it has lots of security bugs), I think that it should work, so to be on the safe side I would test to create a new profile.
RE: FCKeditor does not appear in mozilla
Have you disabled something like javascript or the like?
Does the demo at fckeditor.net works for you?
RE: FCKeditor does not appear in mozilla
RE: FCKeditor does not appear in mozilla