Windows Vista Cant access User Accounts

[AndyPub]

I cant access User Accounts (or Device Manager, Systems, Windows Update) in Vista.
All that happens is a screen almost appears for a milisecond then disappears (all worked first night, then stopped)
Anyone else have this problem or know how to fix it ?

[mickronson@ymail.com]

You must be login to the guest account where you have no access to or Device Manager, Systems, Windows Update only the admin acount which is the owner of the computer.