Taskbar and Start Menu Properties Changes don't Stick

OS Vista 64 Home Premium, AMD Athlon 64 X2 Dual Core with 5 User
Accounts (2 * Admin & 3 Standard Users). Have had no problems for
10 months until 2008/03/06.
Since then one of the Standard Users has not been able to save any
changes made through the Taskbar and Start Menu Properties options.
Also the menu brought up when the User 'right clicks' on the
'Desktop', for sub menu item 'New' shows (Empty).

I have changed the User from Standard to Admin but this did not
make any difference.

I could create a new user and transfer all files etc etc but this
is much work and does not establish what may have caused the problem.