I loaded up the 4.0.4 VzW "OTA update" on my VzW GN (sometime in last couple of weeks), and oddly enough I just started noticing what you're describing a couple of days ago. Until this point, only the power button could "wake up" the phone. In last couple of days I've started noticing that the volume rocker does it as well -- actually a bit inconvenient -- I keep waking up the phone inadvertently.
Wondering though if it's my launcher? I've got Apex Pro installed, and also running the latest beta. Any chance it's the launcher?