hmm.. strange, works well on my Mac+Safari combination. Wich version of Safari/OS X are you running it with?
Version 5.1 (7534.48.3)
OS 10.7.1
The number pad doesn't work for me but the keyboard numbers do. I started to debug but was scared off by seeing all the gwt-* class names. ;-)
WinXP Chrome 16.something (dev channel)
Oh, this is enough info to fix it, I think. Thanks. Numpad probably sends different keyCodes than keyboard numbers, and the (hacky) number field doesn't consider them numbers at all. I'll look into this soon.