Thanks for your instructions. Must find the setting to get e-mails when someone posts to a relevant thread ...

(edit: just found subscribe topic button..)
I didn't want to shut down my machine at present (and also re-install 6.1.18 and then back to 6.1.14), so following the instructions fully may have to wait. However when I checked the show log I found it had recorded what I think to be probably useful enough recent historical logs covering boot ups using 6.1.18 and 6.1.14. Just skimming through the 6.1.18 ones with my totally untrained eye I do see some kind of non response logs for 6.1.18 but there again the 6.1.14 log has some reports indicating some audio component issues (but no obvious symptoms on performance - not that I'm using audio).
BTW, while I'm at it, the clipboard function has not worked for a long time. By which I mean doing something like Copy from VM to then Paste to Host. So I just do an elaborate notepad workaround using a shared folder. If you happen to notice anything obvious that I'm doing wrong then ... otherwise just live with it as a minor issue considering everything else i can do with what I think is a great piece of work.