Thank you for the responses.
No, I do not use Roxio software, so that isn't the problem. Nor do I use InCD, so we can rule that out, too.
I've uninstalled Avast and now Autorun is working perfectly again.
It is safe to say that Avast is almost certainly the issue.
I've installed PC-Cillin 2002 - purely because it came with the motherboard; I'd rather use Avast, though, as it has proven to be the best AV product I've ever used - and Autorun continues to work without problem.
The installation of Windows that I'm using is new - re-installed it yesterday because I thought the previous installation was corrupt. Anyway, everything was working until Avast updated itself to the latest version this morning.
Although I can live without Autorun, I do find it extremely useful as I do a lot of CD/DVD/Digital Camera/USB disc swapping. A few seonds here and there soon adds up!
As for McAfee... the person I recommended Avast to had been paying for updates that failed to detect that he had a virus... well, 85 viruses! Needless to say, I was absolutely amazed that Avast did such a thorough job of disinfecting the PC. Many many thanks to the developers!
Eric