You can try login into the product using another Username:guest and Password:guest to check whether you are able to access the product. If you are able to login, then the possible reason could be that you would
have changed your " admin " password.
If you are not able to login with " guest " user also, then the possible reason could be that the mysqld-nt.exe process got killed.We have faced this problem when running our product in Windows 2003 SP1.
The problem is mainly related to Mysql. We have not got fix for this problem. Do get back to us if your case is similar to the above mentioned one.