You can get the answer to (almost) any problem on Google. I was so impressed with the last example of this, I had to share.
Gmail stopped loading on my laptop. Firefox had just updated but it was still working on my main computer. It was just flickering and reloading and frustratingly blank, though I could see the message headers on RSS feeds. It was also working on Safari but I didn't want to have to start switching to that, thank you very much.
The solution? Clear all your cookies and page history. You don't need to clear passwords.
So if it happens to you, you'll know what to do.
And that's why we all rely on Google...