Unexpected appearance of Windows WaitCursor

I don't do anything with the cursor such as WaitCursor so it's not my code.

I have a datagridview. It's not bound to any database. I just use the datagridview because it's a handy way to display text and numbers in a nice table layout.

But occasionally, for no reason at all, windows changes the cursor to the spinning waitcursor thing when the mouse is over the grid as if the grid itself is doing something.

So, only when the pointer is over the grid. Not when the pointer is over any other parts of the form.

There's no mouseover event. There's no code running or anything so I have no idea why the waitcursor should appear. It doesn't always appear. I can go for days without seeing it. But when it appears it's always there when the pointer is over the grid. Only way to get rid of the wait cursor is to close the form.

I've read about a few cases where developers have a problem after setting the waitcursor while doing long tasks and then finding that they can't unset it again. In my case though I never touch the cursor. The grid's doing it on its own.

Any ideas ?