The crash report you gave is very one-off and not descriptive enough to work with. Do you have 4-5 more recent ones?

Go to Help > Troubleshooting Info and click the about:crashes link

Hello and thank you for your reply!

As I am not very computer literate, I do not know what "one-off" means. I also followed the steps from the Mozilla help page (Firefox crashes). It said to copy and paste the latest crash report, which I did, so I am not sure what you are asking for. Here are Report ID numbers going back to Feb. 12, 2012...

bp-6d913414-01cf-43fd-9074-c884b21202162/16/122:48 PM
bp-5739fee5-1c71-4f7e-9153-eac9c21202162/16/1211:26 AM
C76AA32F-C7C2-46E5-A4EF-A4897B2AC92B2/16/1212:01 AM
bp-329cb007-3c5f-4efa-b905-d508821202162/15/1211:48 PM
bp-c6a6ca8c-1003-48aa-903e-11f3c21202142/14/122:49 PM
bp-dd58ea19-584b-464a-917e-be6f921202142/14/121:53 PM
bp-e278a392-2066-4ac9-ae47-33d4d21202142/14/123:07 AM
bp-1e7fd81b-0a23-4c52-a01f-9ce2e21202142/13/127:18 PM
bp-f80f8061-4ec2-4237-ba3e-c3e0421202132/13/123:39 PM
bp-6b9698bb-6a1e-4731-a3b8-9131f212021

Hmm.. no two of those crashes have the same signature so something is really weird. What's likely happening is that something is corrupting a piece of Firefox memory but Firefox hobbles along until it REALLY breaks and then it crashes in a random place. The problem is that by the time the crash happens, we've lost all information about what caused the corruption in the first place.

(When I said one-off, I meant it looks like no other crash that was submitted but given the other reports, that makes more sense)

There are a couple things that can cause these random crashes: add-ons, viruses, security software are the most common. Since you're on a Mac and viruses are very uncommon, I'm inclined to think it's the security software trying to tamper with the Firefox process.