Vista Standard User logon problem

When Standard users are attempt to to log on, an error message occurs stating "Windows could not connect to the System Event Notification Service."

The problem does not exist for Administrative users.

Raising the account to administrator status allows the user to log on but when the account is changed back to standard the problem reappears.

Several different forums suggest solutions but they do not seem to work.

It has been suggested the problem relates to the Windows update KB930857

Does anyone have a confirmed solution?

Thanks for any help