Can't access any user accounts except administrator

I've been running Windows XP Home for about a year now and *all of a sudden*
all accounts except for the admininstrator account are inaccessible. When I
try to log in to any of the other accounts an Explorer.EXE dialog box is
displayed bearing the message "The application failed to initialize properly
(0xc0000022). Click on OK to terminate the application".

When I click the OK button, I am left with a blank (blue) screen.

Another symptom is that additional directories have been created in
C:\Documents and Settings bearing the names of all of the affected accounts
but with the computer name appended. For example, the name of my computer is
500MHZDELL and one of the accounts is named Jaymie. In the C:\Documents and
Settings directory there is a Jaymie directory and now, ADDITIONALLY, there
is a directory named Jaymie.500MHZDELL.

Yet another symptom is that when I create new user accounts I cannot log on
to them. I get an error message telling me that the account does not exist.

ANY IDEAS?

Thanks,

Frank.