Add new user error

[mk craig 42]

it says this in 'add new user' in the admin panel

Warning: array_merge() [function.array-merge]: Argument #1 is not an array in [path]/admincp/user.php(544) : eval()'d code on line 11

could anyone help?

[snakes1100]

Disable any hacks/addons you installed that relate to users.