I know this one might not quite be an issue of yours, but I can see source code line numbers go "out of sync" with the actual code when I scroll down a source file of more than a 100 lines of code. Internet Explorer 10.0.8400.0 Release Preview and Opera 12.0 display stuff correctly, so my guess is that this is an issue of Mozilla's.
Firefox 13.0.1 once again.