Ok,

iam on a DIR-825 with password (latest firmware DIR-825_fw_revb_201EUb17_ALL_multi_20091019).

Clean pc start, start jd with this script above from shmizan & with user: Administrator & pass: blah, reconnect doesnt work.
Login with FF to DIR-825 webinterface, jd reconnect works with user & pass settings, close FF, wait over 30min, clear user & pass settings in jd and reconnect works!!

strange..