Please see below for commenen issues with the Mozilla Firefox web browser.
Firefox cannot use the profile "default" because it is in use.
Firefox locks a profile when it is in use. Sometimes, when firefox crashes, the locking information is not removed. Hence, at the next start, firefox will falsely assume that the profile is still in use. To resolve the issue, remove the two corresponding lock files. The lock files are named "lock" and ".parentlock" and are located in your firefox profile directory which can usually be found like this:
cd ~/.mozilla/firefox ls
The profile directory is named similar to "x274kdun.default". cd into that directory and remove the two lockfiles.
cd "profiledirectorynamewhichyoufoundoutwhichlookslikex274kdun.default" rm lock .parentlock
See also http://cybernetnews.com/helpful-tip-firefox-profile-in-use/
Bookmarks disappeared
Sometimes when firefox crashes some of its data files are corrupted which causes the bookmarks to be lost. In order to access the bookmark backup, you need to recreate some of those files.
- cd into your profile directory, see above.
- close firefox
ls *sqlite* mkdir old mv places.sqlite places.sqlite-journal old
- sometimes, other sqlite files are damaged, too. You may also try the same with the formhistory.sqlite files
- start firefox
select Bookmarks -> Organize Bookmarks -> Import and Backup -> Restore
- select one of the backups
- start firefox
For more information, please see here: http://kb.mozillazine.org/Bookmarks_history_and_toolbar_buttons_not_working_-_Firefox