[Plugin: Theme My Login] TML 6.0-beta1 uninstall fails

I have disabled all plugins but sill get this error when uninstalling:

Fatal error: call_user_func_array() [function.call-user-func-array]: The script tried to execute a method or access a property of an incomplete object. Please ensure that the class definition "Theme_My_Login_Admin" of the object you are trying to operate on was loaded _before_ unserialize() gets called or provide a __autoload() function to load the class definition in C:\xampp\htdocs\wordpress\wp-includes\plugin.php on line 395