Just lost my Firefox session after a restart. Apparently, it had problems parsing the
sessionstore.js file. While I didn’t fix that problem, I found out how to get firefox to be much more verbose about what it does. You have to set an environment variable, and then firefox will spit out a whole lot more on the console than it usually does.
tiefpunkt@tiefpunkt ~ $ export NSPR_LOG_MODULES=all:5 tiefpunkt@tiefpunkt ~ $ firefox > stdout.log 2> stderr.log