Hi,
I confirm this as a bug. It had been reported previously and I thought I had fixed it before but yesterday I investigated it again and found it still had a bug in the change password format routine.
This is fixed now in svn trunk and will be fixed in the next release of mojoPortal.
Unfortunately there is not a way to do it manually from SQL because we use a .NET method for the encryption and it relies on the machine key of the web app.
Thanks,
Joe