(This is to get this knowledge into the Google cache more than anything else.)

If you are seeing Office applications (Word, Powerpoint, Publisher) hang when trying to insert WMF clipart from Web Collections AND your network is protected by a TippingPoint IPS device, check with your network people about signature 4054. If your IPS is running with the recommended ruleset, all WMFs that cross the device are being blocked and the Clipart manager doesn’t handle that well. The error that is returned is something like ” 0x800c000c “.

I’m guessing they rushed the signature out the door to be the first to post a press release about protecting their customers. Hopefully they will fix the signature in the future.