The "crash" you're seeing is X dying it's not Mozilla's fault. You should report it to redhat/fedora (https://bugzilla.redhat.com/bugzilla/). Can you give more specific steps to reproduce the JS Console problem (before X dies)? Perhaps more importantly, what build are you using?
what theme are you using?
Interesting question. I just got a chance to try it. With the latest build (2004101106) I get the crash with the Modern theme but not with the Classic theme! How did you ever know that this would matter?
I was actually hoping that you'd say you were using a 3rd part theme, but the theme specificity is still interesting. Have you filed a bug with redhat? Are you using an XFT build? (see about:buildconfig)
I was not using an xft build, but the last RPM from Fedora is an xft build (1.7.3-0.2.0) and that does NOT show the problem (but it also does not allow scrolling with the arrow keys in the JS console). However, I just tried to replicate the problem with the very latest build, and the problem seems to be fixed, perhaps as a side effect of some other change (2004101306); again, this is not an xft build. Moreover, the arrow keys work. (By the way, if you want to test this quickly, go to www.nytimes.com and read a couple of articles. The console quickly fills up with error messages, enough so that they do not fit in the largest possible window.) I will try a few more builds, but if nobody else reports this, I will eventually try to change it to FIXED. (Not sure I have permission to do that, but I'll try, if it indeed stays fixed.) I did not yet file a bug with RedHat, and now I probably won't. The newest version of Gnome did "zap" but without lousing anything up. It isn't clear where that bug was (gnome or xorg).
> eventually try to change it to FIXED. Actually, "FIXED" is reserved for bugs fixed by specific patches. "WORKSFORME" would be more appropriate for this bug. see also https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=121403, which matches some of the conditions to crash X, but not all (unless there's binary garbage at NY Times or in your JS Console.