i'll post the ticket right now ;)
"enter" triggers form submit in most browsers - looks like we didn't overload the onsubmit event properly - definetly a bug, thanks for reporting!
fixed in http://open.silverstripe.com/changeset/57395
@dospuntocero: thanks again for opening a ticket - can you please post the ticket URL here next time? and optimally the URL to this forum post in the ticket comments. its way easier to keep stuff together this way.
I also received this error when running php with suhosin security patch. Fixed by increasing settings:
suhosin.post.max_vars and suhosin.request.max_vars in either php.ini or (for ubuntu) /etc/php5/apache2/conf.d/suhosin.ini
Default values where 200, I increased to 10000 and problem went away.
Hopefully some help.