Comment 16 for bug 428703

Just so you know, I've had this bug since I installed Ubuntu 6 months ago, on every version of Firefox and every fresh install of Ubuntu I've done on every system.

If you quickly type gibberish in the address bar, once you reach a certain length, it will stop highlighting, allowing you to type what you want and then delete the initial characters.

It's a pain but hopefully the bug will be fixed soon and at least for me, after a few minutes the issue goes away.