There is an online FAQ which contains the solution to this problem. Basically, you'll need to look in your computer for .pra files. Try to rename the files used and then restart the server.
- rename the file windows.pra to windowscorrupted.pra.
- rename the file windows2.pra to windows.pra
If you still encounter errors, rename the file MMDDYYYY.pra to windows.pra where MMDDYYYY is month-date-year.