As a heavy VPC user on my laptop, I've seen the problem with VPC not responding after the laptop resumes from hibernation. And there's a KB fix: Virtual PC 2004 and any virtual machines may stop responding after the computer resumes from hibernation is the KB article.
Unfortunatly this appears, at first sight, to not be a free update. In order to get the fix, it appears that you have to agree to pay £35 (plus VAT) before you can even DESCRIBE the problem to Microsoft. While I appreciate MS's need for extra income, this is poor: a known bug, a known fix, and I still have to pay just to get it? Sure, the fee should be refundable - but why should I have to pay up front (and trust Microsoft later to refund my fee)??