First of all, computers have a mind of their own. That's why I don't think ANY HTPC (laptop or desktop) is for the mass market.
Second, I think it is related to how you are setting up the Audio Device in Windows.
When you hook it up to your receiver, make sure the laptop Audio Device is set to HDMI Audio as the Default.
Third of all, computers have a mind of their own.
Oh, sorry, did I already say that?
I have a $1,200 HP blu-ray laptop that does that at times too, so I feel your pain!
Sometimes I just reinstall the operating system and it fixed it.