Forum User gets database error on login
 

We recently upgraded our forum from 3.8.4 to 4.0.1

Everything went smoothly but one particular member gets a database error straight after login, only this member that I know of so far.

I've had him try to login at a different location and its the same result. It appears to be just his account.

Whats the best way for me to rectify this?

thanks in advance.