Start menu display of documents as a menu ceases

Start menu display of documents as a menu ceases to function properly on my
new x64-based PC with Microsoft Vista Home Premium operating system.

The capability of opening a document four or five layers of folders deep by
navigating to it from the start menu and clicking on it ceases after opening
one or two documents. In the failure mode the next layer of folders opens
upon moving the cursor to Documents on the start menu, but no highlighting
appears when the cursor is moved onto the newly displayed layer. Clicking on
the layer without highlighting closes the entire start menu. Right clicking
on Documents and selecting Explore still opens Windows Explorer. Upon
restart the proper cascading menu function is restored until it is used.

In this failure mode all start menu items set for display as menu perform in
the same manner, including the bottom menu (Log Off, Restart, Shut Down,
etc.). Normal shutdown sequence can be initiated by using CNTL-ALT-DELETE
and Log Off as a work-around.

What steps should be taken to restore full-time start menu functionality?