Did you try a new profile?

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

Yes, I tried that too, but Firefox still crashes :(

Type about:crashes in Firefox and paste here some recent IDs of crash reports. And post the list of your add-ons/plugins, please.

There is a crash ID posted in the system details list: [@ ia@0x6bafb ]

• https://crash-stats.mozilla.com/report/index/de38274b-719c-4859-af1f-e12c72120423

Also, I don't have any plugins or ad-ons installed.

The signature shows a problem with IA.

Do you have any idea what that 'ia' application is part of?

Sorry, I have no clue what the 'ia' application is associated with.

I found an earlier version of Firefox (8.0) from a time machine backup, and it seems to be working just fine, so I'm curious to know what has changed from 8.0 to 11.0 that is causing this crash on my system.

https://support.mozilla.org/en-US/kb/Firefox%20crashes

Already followed those procedures finitarry. That's how I ended up in here after reaching the section on "Getting help fixing this crash."