Win XP Pro can't type into password boxes on login page
 

Win XP Pro, latest updates. One Admin account, 2 user accounts
Dell Dimension 4400 bought second hand, with Dell OEM version of XP Pro
which I installed, along with new Dell sourced memory (1GB), and
including Dell drivers etc. at time I set it all up. No other problems
encountered.
Sunbelt VIPRE antivirus, ZoneAlarm free firewall, Secunia update
adviser, OpenOffice, Firefox, Thunderbird. Updates carried out regularly.
Defraggler, CCleaner used to keep it tidy.

When I log out of one XP account back to the login screen, the login
password boxes for the 3 accounts don't show a cursor and won't accept
text input. So I have to restart the machine at which point the password
boxes work again. Till next time.

Machine is set to start screen saver if left, requires login password to
get back into the XP account.

Many thanks in advance.
--
Robert