Why would AMD cover 2.4GHz errata when that's outside their 2.2GHz/2.3GHz warranty and never guranteed by them?

The errata is present in the silicon. It will never manifest itself at normal loads or usage. When you run a certain application with very unusually high loads, you will experience it. If yuo run those sort of apps, then you need the patch -> or else, no.

I'm running WCG 24/7 since 2-3 days at 2.42GHz and 1.98GHz on NB & HT. No problems whatsoever, no errata. The lockups are because these retail chips simply seem to have a speed limit.

That mainly, or, less likely, the BIOS is very bad yet.