I came across a firebug error, "SyntaxError: syntax error " which took me a half an hour to crack, so hopefully I can help you not waste half an hour yourself!
The bug looks like this:
I googled and found out that it might be caused by a script-tag not having a src-attribute. But all my scripts have that! So... I ran it through fiddler, and lo and behold, it turns out the page couldn't even load my script - because I was doing an old-fashioned asp.net solution and I hadn't included the scripts-directory in my locations, doh!!:
Once I did so, case was closed. So the bug was between the keyboard and monitor...