Admin Login stopped working + error of forgot password page

Hi,

I am using OC 1.5.1 and everything was working fine until I tried to login to my admin panel today and got a "No match for Username and/or Password." error. So I used the forgot a password feature but when I entered my admin email address I got this error message:
Error: Unknown column 'code' in 'field list'
Error No: 1054
UPDATE `user` SET code =.......

I double checked that my admin was the correct one by looking at the table 'user' through PhpMyadmin and right enough the correct email address is in there.

I then used this plugin http://forum.opencart.com/viewtopic.php ... ord#p76531 to reset the password.

However, I am still having the exact same problem. Any idea what went wrong? or how I can fix it?

Thank you very much for any help