Well, I am so sorry, i've just tried it once again, and now it works! Believe me or not, i've tried it a couple of times and it did not work. I even had a look at the table UserProfile, but the data was not saved. Then i changed it into a radiobutton list and it worked.
Now i changed it back into dropdownlist to test it again, and everything gets saved now.
I don't know what happend or what i was doing wrong. Sorry once again.
The next time I try longer before i write here