Login and Authenticate Problems

This is the timeline:
1 Installed Ubuntu 11.10 with password A
2 Play with the system a little...
3 Reach "User Account" Settings
4 Use password A to unlock and change login with password to no password (Here's where the problem comes)
5 Restart to see effect
6 Logged in but needed Authenticate because I DIDN'T USE PASSWORD TO LOGIN... (weird option above)
7 Wanted to changed back to need password
8 Logout Login and THE SAME
9 Change password A to password B and the login with(out) password
10 Logout Login Authenticate Failed. password not match?! (but I changed the password)
11 (The funny thing) try, try and try again with the password B and the Authenticate Window disappered?!
12 Search for options on web, used (reboot > recovery mode > command: ls /home > command: passwd user(my name)
13 Logged in and try again for that login with password
14 Changed password A to password C but the "Change button was disabled (cannot click?!)
15 THE PASSWORD SYSTEM MESSED UP sometimes pass A works, sometimes B and C????!!!!!!
Help

*For Testing I made another account and changing the password and login with(out) pass works, is it a bug?