Alright, I upgraded to version 5 a while ago:
7/31/2010 12:42 AMThank you for your purchase from our online store, operated by element 5.
Your new license for avast! Internet Security 5.0 (3 PCs, 1 year) is
attached.
It worked beautifully, as it should, until suddenly today… It says that my key is invalid when I try to apply License.avastlic.