I have two theories currently.
1.) The only time the "coma" lockup has occurred for me is while the phone has went to sleep while running an app. For instance I was using the headphones to make a phone call, the call was working fine, I hung up and then couldn't get my phone out of sleep mode. The other instances in which this has occurred have happened while listening to Pandora and then letting the phone go to sleep. Pandora plays fine, I can even stop and start it with the headphone remote, BUT I can't get the screen to wake up when this occurs. I can connect it to my macbook and access all the files via iTunes, even move media on and off it, BUT the screen stays black OR shows the Apple logo frozen and either restarts on its own or I have to force a restart.
2.) I got the phone brand new and restored from a backup of my iPhone 3G. However the iPhone 3G was running OS 3.1.3. I had not upgraded it to 4.0 before backing it up. I then "restored" the 3.1.3 backup from the 3G onto the iPhone 4 when I got home. I have a hunch that the differing OS versions might have left over some uncooperative scripts/settings in the backup I used on the phone.
Did anyone else who is experiencing this problem restore from a backup made on a phone running any OS before 4.0? I'm going to test this out tonight. I'll wipe the phone, upgrade the 3G phone, back it up, and then move that backup onto the "clean" iPhone 4.
My assumption is that this isn't a hardware issue, it is a software issue. As others have indicated getting a phone replacement and the error still occurring. Further tests have revealed from my end that the phone is in fact "awake" but the screen won't turn back on.