What message exactly is it giving you when it's checking an email address? In addition to the message what color is the box (green, red, orange)? Sometimes a mail server simply can't be reached and will result in the check failing; does not mean the address is invalid, but instead "appears" to be invalid.

The color is orange and the message is "could not check this email: please double check. Needed for confirmation".

This would mean the mail server didn't respond to the validation check. A lot of private providers don't or if a mail server is experiencing heavy traffic, etc.. the response will be denied for performance reasons. It's no means a guarantee. Try an @yahoo.com address or something of the sort.

It does this at all new registration. Sadly, i've turned off the email checker since I figured that feature is a problem and it still trys to chekc the email address. So, the config change in global config doesn't work either.

This only disables for frontend; backend will still ajax check.

You're welcome to review cbCheckMail inside of comprofiler.class.php and make any suggestions you feel necessary. If the PHP function getmxrr is disabled or not available for instance then the check will always fail. It also needs SMTP in order to check a users email address.