Update: fixed in v19.0beta (at least v19.0b1 build3 looks good):
ftp://ftp.mozilla.org/pub/mozilla.org/firefox/nightly/ (19b1 does not save sessions, though 😉
Firefox 18 (all betas and 18.0) crashes on Solaris 11 and OpenSolaris. The workaround is to set the following variables to “false”:
browser.cache.disk.enable browser.cache.memory.enable browser.cache.disk_cache_ssl
See bug 827971.