Firefox 28 randomly crashing for the last three days

I re-enabled HTTPS-Everywhere last week and haven't experienced any crashes so far. There have been several updates over the last four months, so maybe one of those fixed it. If I manage to get to the end of this week without any crashes, I'll mark this as solved.

Update: I think I can go ahead and mark it solved now, actually. After HTTPS-Everywhere updated back in April, there were three things that would cause Firefox to crash: restarting after enabling the add-on, restarting with tabs saved, and visiting certain websites such as the Tumblr homepage. I've been able to do all three of these over the last week without Firefox crashing, so I think it's safe to assume that whatever was causing the crashes has been fixed in one of the updates since April. Thanks for all the help and advice in this thread. It looks like it was one of those problems that solved itself over time.