Implementation of hook_uninstall().

autoassignrole.install
line 6 column 44

<?php
/**
 * Implementation of hook_uninstall().
 */
function autoassignrole_uninstall() {
	$vars = db_query("select name from variable where name like 'AUTOASSIGNROLE_%%'");
	while ($var = db_fetch_object($vars)) {
		variable_del($var->name);
	}
}

You must replace variable by {variable}