I am having the same problem.
I'm actually not very impressed with XAMPP at the moment. I have been doing web design for 11 years and have over 20 years setting up and installing programmes, so I am completely flummoxed and getting very frustrated.
I set up XAMPP fine, put all the passwords in place and went into localhost/phpmyadmin for the fitst time and it said that I hadn't given MySQL protection (I had) but to go back and put the security in place. So I did this and now cannot get into phpmyadmin for love nor money.
I downloaded XAMPP 2.1 today.
I've been getting error "1045 using password YES and NO" whether I put the password in or leave it blank.
I found a tip online to enter the password manually into the config.inc.php file which I did, but this didn't work either.
I have just tried the tip here to type 'root' as user name and leave the password blank - still didn't work.
Please can someone help?