Never mind.. I checked again and it fixed itself

God damn... and now it seems to have gone again.

Some of the time the friendly blinking line in the edit box is gone, but just now it came back again

Could be that it's only working the first time I edit a post - both times that it had disappeared were second edits

<edited> nope, first edit of this and it's gone again

Yeah, it's a know bug Super-King. Looks like a problem with FF and input fields. Works fine in IE and Safari.