Opencart error when registering

In checkout process while making a new account I get a error message. This msg pops up in a new window: [login to view URL] This message comes when I press Continue (fortsett). I think it could be some problem with the Advanced Customer Groups module. When I uninstall the module and install it again, this msg comes: Duplicate column name 'group_code'. Error from log file: 014-02-05 0:04:22 - PHP Notice: Undefined variable: produk in /customers/9/8/b/[login to view URL] on line 541 2014-02-05 0:16:42 - PHP Notice: Undefined index: customer_group_code in /customers/9/8/b/[login to view URL] on line 6 I hope someone can do this on a very small budget. I also would like someone to start now.