So you don’t like the now-changed hardware mute switch on iOS 4.2.x for iPad and want to turn it back into orientation lock? Well there is now a jailbreak app for that ! , which changes the mute switch functionality of the hardware button back to its original orientation lock mode from iOS 3.2.x (for iPad) era.
You will, of course, need to have a jailbroken iPad on iOS 4.2.1 to install it.
NoMute is available from Cydia for free under BigBoss repository.