Firefox 28 search is easily interruptible When I search on a Firefox page (command-F) the search interrupts itself all the time.

E.g., I start typing "backtick" and, right before I hit t, back disappears and I am now searching just for t.

On the other hand, sometimes the search prompt in a tab persists: I go to another tab, and, when I get back to this one, the search prompt is still active with the old text in it.

This behavior started when I upgraded to FF28 a couple of days ago, however, I seem to recall that I experienced this sort of annoyance some time in the past.

Any idea what might be causing this?
Removing the extension "fast video download (with search menu)" solved the problem.