IIc Mouse not moving vertically

[Myles.Fudge@logicbbs.org (Myles Fudge)]

Lately my IIc mouse have not being moving vertically... only horizontally.  The
mouse pointer moves across the top of the screen okay, but it is stuck on that
line.  I have been testing my mouse with ProTERM v3.0.  And this is the mouse I
have had for years.  I notice that the mouse pointer character flickers if I
move the mouse vertically, but the pointer stays on the top line of the screen.
 I have tried two different mice and I assume now that the problem is with the
IIc and not the mice.  Does anyone know of a common problem that prevents a IIc
mouse from not moving vertically?

Myles