thanks for your reply.
How would I get the ADMIN-ID using WWW::Mechanize?
And I SOLVED THE PROBLEM!!!
It wasn't in the HTML I took out.
I used 'LiveHTTPHeaders' to see what's realy being sent and received. That's when I noticed that the last character of my password is cut off.
I ajusted my script, deleting the last character of my passwort and BANG! it works. :-)