Error warnings

When creating an new account - I get this

• warning: array_fill() [function.array-fill]: Number of elements must be positive in /content/HostingPlus/b/a/barterbods.co.uk/web/includes/database.inc on line 253.
• warning: implode() [function.implode]: Invalid arguments passed in /content/HostingPlus/b/a/barterbods.co.uk/web/includes/database.inc on line 253.
• warning: array_keys() [function.array-keys]: The first argument should be an array in /content/HostingPlus/b/a/barterbods.co.uk/web/modules/user/user.module on line 502.
• user warning: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near ')' at line 1 query: SELECT p.perm FROM role r INNER JOIN permission p ON p.rid = r.rid WHERE r.rid IN () in /content/HostingPlus/b/a/barterbods.co.uk/web/modules/user/user.module on line 502.

Any ideas?