Can you determine what causes this problem?

The custom statuses are causing the problem. The function user_get_assigned_open_bug_count() has the following SQL query:

$query = "SELECT COUNT(*)
FROM $t_bug_table
WHERE $t_where_prj
status<>'$t_resolved'
AND status<>'$t_closed'
AND handler_id='$c_user_id'";

I agree with this problem and think the sql query is wrong. I have a custom status "tested" between resolved and closed. I think the sql query should only select status beyond resolved and not above like:

$query = "SELECT COUNT(*)
FROM $t_bug_table
WHERE $t_where_prj
status<'$t_resolved'
AND handler_id='$c_user_id'";

fixed in CVS. Removed hardcoded "RESOLVED" as well.