In an apparently random manner, my mouse pointer changes to an icon
that is not even present in the mouse scheme!

When I mouse over, for example, the toolbar portion of Excel, my mouse
cursor changes to the pointer with hourglass (i.e. "wait") icon.  My
current "Working In Background" icon is set to the pointer cross-hair;
the pinter with hourglass is not present anywhere in my current mouse
scheme.  And the behavior is random:  sometimes mouse-over toolbar
causes the change, other times mouse-over .cs file in edit mode of
Visual Studio causes it.  Not only is it annoying but it makes it
difficult to work.  For example, when editing code in Visual Studio, I
expect to see the vertical "beam" whcih makes it easy to click where I
want to edit.  It is also difficult to autoFit columns in Excel
because the poniter is bulky.

Any ideas appreciated!