Firefox seems to use the system profiles by default (even for other monitors!); this matches my experience that I talked about the other day. Same thing for me: a profile was auto-generated and I did not know about it, and it provided really strange results (too warm, in my case).
As pointed out by Kofa, there are about:config options in Firefox to stop it from loading that profile, but the most radical approach is of course to disable the profile system-wide.