If you can login to the help desk (https://helpdesk.psd150.org), then your password is ok.  psd150.org sign-in uses your last name + last 4 of SSN and the same password you used to access the help desk.

If you still can't login to psd150.org, you should try clearing your browser cache.  Instructions for different browsers are listed below:

For Google Chrome: http://support.google.com/chrome/bin/answer.py?hl=en&answer=95582
For Firefox: http://support.mozilla.org/en-US/kb/clear-cache-delete-temporary-files-fix-issues
For Internet Explorer 8: http://kb.wisc.edu/page.php?id=12314
For Internet Explorer 9 & 10: https://kb.wisc.edu/page.php?id=15141

Please try that and see if you can login to psd150.org.  You may also want to try a different browser as well.