Hello,
I have the same error on frontend, after form is submitted:
Notice: Undefined offset: 0 in /www/doc/test.mydomain.cz/www/plugins/cck_field/group_x/group_x.php on line 392
Warning: Invalid argument supplied for foreach() in /www/doc/test.mydomain.cz/www/plugins/cck_field/group_x/group_x.php on line 508
Can you please write me, how you have solved the problem?
Thank you in advance!