Could not complete you request because it is not a valid Photoshop document.

Since upgrading to PS CS6 I too frequently get the following message when yrying to open a document:

"Could not complete you request because it is not a valid Photoshop document". This never happened in CS5 and this is the 3rd or 4th time in CS6. The documents are quite simple. Only a few layers - just slightly adjusted photo graphs.