You mean you can't log back in? Are you seeing garbage characters for username in the pulldown menu to login? This happens when switching between USA ane Euro firmware (which both run on "Western Region" NVRs). What happens is that the Admin and User account database becomes corrupted (or in actuality is encrypted and stored in the NVR differently) when switching between certain firmwares. The fix is rather simple:
1. Get to where you can login from the NVR console and see the garbled junk characters as usernames. First try selecting the first garbled username and use a blank (null) password. Check to see if it logs you in with admin privileges by going to the configuration menu. If it doesn't then logout (you may need to reboot) and repeast the same procedure with the second garbled username and a blank password again. Repeat by going down one username in the pulldown each time until your in with admin rights.
2. Then go to the Maintenace menu and reset the box to factory defaults