UPDATE: The early event triggering seems to happen in both IE8 and FF4. For some reasoin, although I was getting two alert notices in FF4, I cannot reproduce that behavior. Also, in both cases, seems like no params are being pased in.

PREVIOUS COMMENT WAS: Actually, to add: IE8 fires once when entering the cell, before the text gets converted to a textbox. In FF4, you get that incorrect behavior and also the apparently more timely post-edit. So, IE8 does it once at the wrong time, and FF4 does it twice, once wrong. (And, in all cases, all params like celname are undefined.)