I realise this is over a year old. Nevertheless I have just encountered exactly the same issue, even down to the "PCH?" text in the .coverage file and have found no solution up 'til now. But surely someone else has had the issue too so, just in case, here's the simple solution:
After checking this MSDN link and following its advice I still had the same issue. So, in the end, I shutdown VS, went to the root solution directory and deleted the .suo file. It has the hidden attribute set so you might need to set explorer to show hidden files.
Restart VS and re-run the code coverage tests. All fine.
与恶龙缠斗过久,自身亦成为恶龙;凝视深渊过久,深渊将回以凝视…