Jerome,
Sorry about the delay in replying; I’ve been really ill and unable to use the computer.
Sorry also for creating a new thread rather than replying in my original one, but the forum wouldn’t allow me to reply; it kept saying I couldn’t reply until I’d logged in, even though I’d logged in repeatedly. It did this in two different browsers and after a reboot.
Anyway, the problem seems to have resolved itself, and as far as I can tell, it was caused by another piece of software anyway, the one I was using to get a nice piano sound (iGrand).
So thanks for trying to help me and wish me luck!