After an upgrade wine wouldn't open anything, not even the pre-installed notepad.
There are no wine logs and nothing is mentioned in any standard log file about why.
I finally decided to run wine from the shell and see what's going on:
wine client error:0: version mismatch 398/402.
Your wineserver binary was not upgraded correctly,
or you have an older one somewhere in your PATH.
Or maybe the wrong wineserver is still running?........