Selecting folder on external drive closes finder window

Please help. I'm low on scratch disk space and trying to move files over to an external drive. Suddenly I started having trouble with one folder that I've been copying files into on that drive. When I try to open the folder, it closes the finder window completely. I've verified the drive via Disk Utility and it says it's OK. Any guidance in figuring this out would be very much appreciated.

I'm on an iMac running Lion 10.7.5