I touched the address bar sometime in the last week, and it's doing a funny thing where the URI appears twice. I need to go back and review all the changes I've made. (And to remember that just because the code looks right or consistent doesn't mean that it's correct...)
I can't get this bug to show this morning, stressing it on Windows, Linux and a Mac. I believe the code change was at svn version 18021, where I made pressing enter in the address bar identical to pressing the green "go" button.
I've seen this recently again, it hasn't gone away.