Let's try to start Firefox in Safe Mode, does that help at all? Also, try reading the article Firefox crashes, it does have some basic troubleshooting that you can try to see if it helps.

Looks like a problem with writing to disk (startup cache?)

Create a new profile as a test to check if your current profile is causing the problems.

See "Basic Troubleshooting: Make a new profile":

• https://support.mozilla.org/kb/Basic+Troubleshooting#w_8-make-a-new-profile

If that new profile works then you can transfer some files from the old profile to that new profile, but be careful not to copy corrupted files.

See:

• http://kb.mozillazine.org/Transferring_data_to_a_new_profile_-_Firefox