Cannot Log Into Windows 7 With Passwords

I have been running my Windows 7 Ultimate x64 system for over a year now with no problem. When I tried starting my system today I had this strange problem. I have 2 Admin accounts and one Std. user account set up. I usually use one of the Admin accounts I will call Admin-1. When I entered my password this morning to log in I get an "Invalid Password" message so I try all the normal things - is caps on, scroll, etc. I am sure I am typing it in correctly so I try logging in with the backup Admin account - Admin-2. I also get an Invalid Password error even though I KNOW I am putting in the correct PW. Finally I go in with the Std User account which does NOT have ANY password on it (luckily). Once in I go to User Management in the Control Panel and I get prompted for an Admin account and PW. I use Admin-1 account and the password which WORKS. I reset the PW on Admin-2 to a new password but when I try to switch users to the Admin-2 account I still get Invalid Password. Next I remove the password for the Admin-2 account then I am able to switch over to that account. I try changing the password on Admin-1 but when I try logging in I still get Invalid Password.

I do not want to remove the password on my primary Admin-1 account due to the warning message I get when doing so to the effect that I will lose all saved passwords and other goodies.One other thing worth mentioning is that when the PC was last on my virus scanner found and 'treated' a slew or trojan/viruses in my temp Web directory. It looked like everything was honkey dory when I logged off. I also did another scan from the Admin-2 account this morning and nothing was found.