What steps will reproduce the problem?
I can't reproduce it. It happened when I was exiting Spaces (I think).
What is the expected output? What do you see instead?
Normal editor display. Instead, there's a small red dashed rectangle in the middle of the screen. It appears in all tabs/buffers. There's no text underneath it in the buffer it first appeared in.
What version of MacVim and OS X are you using (see "MacVim->About MacVim"
and "Apple Menu->About This Mac" menu items, e.g. "Snapshot 40, 10.5.6
Please provide any additional information below.