amd64, after emerging (updating to) the newest version of mozilla-firefox-3.0.14 (together with net-libs/xulrunner-1.9.0.14) it does not want to run anymore, the error message (when started from xterm) is:
emerge xulrunner wrote:If firefox fails to start with "failed to load xpcom", run revdep-rebuild
If that does not fix the problem, rebuild dev-libs/nss
Try dev-util/lafilefixer if you get build failures related to .la files