I have fixed it thanks to your suggestion.

I went to rename the preference folder, and found that I had already renamed it to, "preference old", due to a previous problem with the metronome.

It hadn't created a new preference folder, but when I deleted the "old" and restarted BIAB it was back to normal.

I just hope that the metronome problem doesn't come back.

Funny thing, this problem only started last week, whereas the metronome problem was a few weeks ago, and it had been running fine in the meantime.

Thank you all for your help.

Regards