Could you please check previous forums post this issue has discussed. However please try this.
1. Reset the password using passwordreset.bat file. File Location C:\ColdFusion10\cfusion\bi, once you reset the password restart the ColdFusion service.
2. Reduce the security in your browser.(in case of IE)
3. Try with a different browser.
4. Try to access the ColdFusion admin from different machine.
5. Try to access using IP address instead of using domain.