Some users could not log in when using Internet Explorer.
I'm aware of this problem and am looking to fix this issue. As a workaround use FireFox - my favorite browser, or click on Forgot password link in the Profile block on the home page. The system will send you an email with a new password and the URL. Click on the URL to login to the site.
Hope it helps.
Fixed - could not log in when using Internet Explorer
the problem with failed logins has been resolved by installing new Drupal module LoginToboggan and upgrading Drupal to version 4.7.4