Hi, thanks for the post. First of all, please make sure that "Allow only the Classic Start menu" is not checked under User Settings – Windows Restrictions. Most likely, this issue can occur if this restriction is enabled. If this restriction has once been enabled, it will retain the setting. We need to disable Windows Disk Protection (if it is enabled), disable all restrictions under Windows Restrictions in User Settings of the shared user. Then, let's log on the shared user and enable Windows Vista aero, log off. Re-enable those restrictions (except "Allow only the Classic Start menu") and/or enable Windows Disk Protection.
Hope this helps!
Sean Zhu - MSFT