strange behaviour on Hardy upgrade

[Lisi Reisz]

Someone whose computer I administer has the following problem (I have not yet 
seen the computer):

This chap runs Kubuntu 8.04.  He uses Adept to do a weekly update to keep his 
computer secure.  On Thursday he went to do his usual update.  Adept reported 
that there were no more security updates and offered a full upgrade to 
Jaunty, but no other options.  He accepted.  Now the system will not allow 
him to use it.  It is asking for the password, but when he gives it nothing 
happens.  The wrong password results in an error message.  The  correct 
password has no effect at all.  When he enters it, the system just goes back 
to asking for the password.

1) There are still updates available for Kubuntu, so what might have caused 
Adept to report that there are none?

2) Why does the password not work?

3) What can be done about it?  Preferably other than reinstall.  He has no 
backup. :-(

TIA,
Lisi