Firefox 28 randomly crashing for the last three days

It started on Tuesday night. I closed Firefox to run a couple of scans with Malwarebytes and Avira (both free versions), and as soon as I reopened it, it crashed and asked me if I wanted to restart it. Every day since then, it's crashed and asked about restarting. I might be wrong, but I'm pretty sure it's always happened around the same time in the evening.

I think my HTTPS-Everywhere extension was updated when I closed Firefox to start the first scan, as the Firefox Add-ons Manager said it was lasted updated on the 15th of April, and the extension's folder says it was last modified about five minutes before I started the scan. Would it be a good idea to try disabling it tomorrow and seeing if it crashes again? I know the update has brought back an old problem where Google Images gives a redirect notice when viewing a full picture (I confirmed it by using Google Images on my laptop both before and after updating the extension, and the redirect notice only started appearing after the update).

Update: Firefox crashed again today, only it was in the afternoon rather than the evening. If it helps, I'll post a screenshot of the window that opens when it crashes next time it happens. I didn't disable the extension because I didn't get a reply yet.

Update 2: Firefox didn't crash at all on Sunday, and almost went without crashing today, but crashed just a few minutes ago. Unfortunately, I forgot to get a screenshot.

Have you tried clicking firefox-help-restart with addons disabled?

Does the problem stay gone after having all add ons disabled?

Thanks for the link. I'll have a read through it.

Update: I've followed the first three steps, but the problem still occurs. I think I'll go ahead and try browsing with HTTPS-Everywhere disabled this weekend. It and Adobe Flash Player were the most recently updated plugins when the crashes began, but Flash updated two days in advance whereas HTTPS updated the day the crashes began (it updated when I restarted Firefox Tuesday evening, and Firefox crashed shortly after restarting it). If the problem still occurs, I'll keep reading for more ideas.

Update 2: I'm actually going to start browsing with it disabled now. Firefox has crashed several times today.

It's been nearly four days since I disabled HTTPS-Everywhere, and I haven't experienced any crashes yet. If I manage to get through the rest of today and tomorrow without any crashes, I'll re-enable it either tomorrow night or Wednesday night and see if it starts crashing again.

Update: Well, identifying the cause of the crashes may not be as easy as I thought it was. Firefox stopped responding a few minutes ago. However, it wasn't quite the same problem I've been having recently. From the 15th of April (when the add-on was updated) to 24th (when I decided to disable it), when Firefox crashed, it would open the crash reporter seen in this attachment. Tonight, it simply froze then said "not responding" until I closed it, which is what I'm used to seeing when Firefox has a problem. I'll keep it disabled for tomorrow and Wednesday. If I don't have any problems, perhaps I can assume tonight's problem was just a coincidence. Otherwise, the extension isn't what's causing the crashes.

Update 2: Just a quick update as I noticed that HTTPS-Everywhere was updated two days ago. I'll stick with my current plan and keep it disabled until Thursday morning.