[nitrous9200]

If you're saying the volume control worked before the full screen volume control update, you can pull it out of the startup sequence and use the built in volume slider (which was the behavior in the original ROM).
Open up your File Explorer, browse to My Device > Windows > StartUp. and look for something named "LargeDisplay". Long press on it, press Cut and go to any other folder (like My Storage) and then paste it there. Then reset the phone and it will not come up anymore unless you move the shortcut back.

ps - instead of staying with the stock software, you may want to poke your head into the world of ROM flashing (Omnia Upgrades section of this forum). These roms have the latest bleeding edge builds of Windows Mobile 6.5 (even newer than the current 6.5 phones on the market) and have other benefits - they usually run faster, get better battery life, and are tweaked to be more pleasant to use. we're all happy to help.