Last night my Firefox browser started to crash. Not occasionally, but every single time I started to to type something in the search bar in the upper right hand corner. What the heck happened?

There are several possibilities when an application suddenly starts getting buggy:
- Gamma rays from outer space changed some of the bits on your hard drive, thereby messing up your software.
- You are having hardware problems, such as memory glitches or hard drive problems, that are causing instability.
- Your machine has been infected with a virus or a worm.
- Some other application messed up a file that the application in question uses.
- You deleted or otherwise mangled a configuration file or (for Windows) a registry entry.
- You installed an operating system update that changed something, and that eventually caused your application to break.
- You installed an update to the application itself.
- For applications that support extensions, addons, or plugins, you added or updated one of those, and it broke your application.
When this bad behavior started, I popped over to another machine running the same operating system and checked to see if Firefox there was broken. It wasn’t.
Next I tried doing the same thing that demonstrated the problem 5 or 6 more times to see if it went away as magically as it appeared. It did not.
Ah, I thought, I bet I have Firefox 3.5! Will upgrading to Firefox 3.6 fix the problem? It didn’t, though it did tell me that several of my extensions were not yet available for Firefox 3.6.
Next I considered whether now was a perfect time to switch to Google Chrome. Perhaps, but that was avoiding the problem rather than fixing it.
I then completely, or so I thought, wiped Firefox from my machine and reinstalled it from scratch. That did not fix the problem.
I wondered … are my old extensions still installed? They were, so evidently my cleanup had been incomplete. I uninstalled them all and restarted Firefox. The problem was gone.
At that point I vaguely remembered that Firefox had asked to install some extension updates and I was so busy with something else that I just accepted it and got on with my work. That was before the problem started. Hmmm.
I started reinstalling my primary extensions and checked after each one to see if I had the problem. I didn’t, but I stopped after five. I suspect the problem was either in Firebug or YSlow, but I didn’t verify. I know that Adblock Plus, COLT, ColorfulTabs, Diigo Toolbar, and XMarks are not causing issues, and those other two extensions are the only ones I did not reinstall.
The moral of this, as with most debugging, is: if you change something and then your system is broken, what you changed caused the problem. It’s not always direct cause and effect, and you may not notice the problem for a while, but it’s good to strip back to basics and then add things in one by one until you can find the culprit.
Update: Consensus seems to be that the update to YSlow is problematic.



You are the 2nd person in 2 days that I’ve heard having crashes and removing YSlow fixed the issue, so I suspect that it is the culprit.
I had the same exact experience with the sudden crashing of FF on my Macbook Pro, just last night. I’d start to type something into the search bar and WHAM!, Crash. I just switched over to Safari for the time being, and have since shut down my machine and will try the suggestion you make later. I remember YSlow being one of about 4 updates that I ‘agreed’ to make just as you had. Bummer if YSlow is the issue, I was looking forward to checking out it’s update.
I had the exact same problem this morning as well. Disabled YSlow and everything is back to normal.