Thinking it was a bug in Mozilla, I have already made a full bug report at http://bugzilla.mozilla.org/show_bug.cgi?id=251142. It was fixed after I changed some settings in my xorg.conf, so I am beginning to believe that it is an XOrg-specific issue.
Please attach your Xorg.0.log from when you're able to reproduce it.
original report sounds like the reported was using 8bpp color and experiencing colormap fighting. notabug. please reopen if you have evidence to the contrary.
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