Cannot type in Tor Browser

As can be seen in the screenshot in the attachment, when I run TorBrowser, it's like Alt is continually pressed: the menu bar is focused and I cannot type. Clicking somewhere e.g. on the page does not help.

Running TorBrowser 3.5.2 (I just tried 3.5.3 as well - same problem) on Ubuntu 13.10.

Trac:
Username: Vincentt