Invalid argument supplied in CCK

Hi,
since i installed Formfilter, i get an "warning: Invalid argument supplied for foreach() in /var/www/web55/html/buschtrommel/sites/all/modules/cck/content.module on line 1284." Error Message on my startingpage. I tried to hide some fields of the "edit an article" form. For me, it is important to take away this Error, so if i can't use Formfilter it's okay but i need to take away this error. I tried to turn Formfilter off but the Error stays. Maybe i can change some values in the database or something like this, so everything is like before?

Thanks for your help! :)