Sorry to enter the discussion, but my issue looks a lot alike.
I too can't save certain files to Gdocs from my offline folder. In my case .png, .psd and .jpeg files give the same error message in my log as above:
"Upload from: E:\example.pngFile Upload - Google server http REJECTED file example.png System.Exception : sd criticality=1 Inner: Source: Syncdocs : sd criticality=1"
I have a regular unpaid Google Apps account.