Disappearing cursor (Inspiron 8500)

[Shinzon]

Hi everyone, I have a Dell Inspiron 8500 and I think there is a small problem with my screen.  You can see everything on it with no problem, its perfect, except that there is one point on the screen where the cursor disappears.  It seems like there is an invisible line that go across the screen (no bigger then a single line of text e.g. size 12 on word)which seems to hide the cursor.  Its like the cursor is hiding behind something, but I haven't got a clue what it is or how to fix it.  Any ideas?  Any help would be greatly appreciated.
Thanks for your help.