Here is the feedback I received from AVS, which is more or less what I expected to hear:
Hello Stuart,
To avoid the described problem we would advise you to use the latest version of AVS Video Editor (version 4.2.1.188). If you have not found the necessary features in this new version of the program, please describe those features so that we could provide you with detailed recommendations.
You purchased AVSMedia Super Bundle on our website
www.avsmedia.com in 2008. We have considerably updated the software and the latest versions of AVS programs are now available on our second website
www.avs4you.com.
Using your current registration keys you can only activate the previous versions of the programs you bought.
But according to AVS upgrade policy, as our subscriber, you can get the Unlimited Subscription on our second site
www.avs4you.com for free. So you will get the possibility to use all the software with updates and also all the new programs from this site. The licence is valid for 1 PC only.
Please download the applications you need from
www.avs4you.com and activate them with your new license key:
...