Today I upgraded my portal from 4.3.4 to 4.3.5. I copy the upgrade package to the proper place. After upgrade , everything work fine. But I found I can't use admin account to login into "my first website". Host and registered user work fine. My second website work fine. Just my first website can't use admin account to login. But the log viewer can't work on my website. Is there any other clue for me to find what's the problem? I used SBS2003 cht version.

ps:after more testing. It seems this problem is user account level?? I can assign another user as the administrator and works fine.

Even I remove the security role of the origional adminstrator to be a normal registered user. This account still can't login. What strange is this account seems totally not work? I can't login. Even I enter a wrong password. It still show error message instead of tell me I need to enter a correct password.(I think this should be the right case if I enter the incorrect password, right?)

The error message is

A critical error has occurred.
Object reference not set to an instance of an object.

One more hint: when I use host account to see the user data. I found the Created Date is empty for this account. Others all have their Created Date.

Can anybody help me?