NSTableView visual issue

Can someone tell me what might cause this white rectangle in the column to appear? T开发者_如何学Pythonhanks.

Thanks!

EDIT: If i resize that table column it goes away.

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It looks like it might be a view floating above the table view.

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Please see this question I just asked. It may be the same problem.

NSTableView redraw not updating display, selection sticking