I have been having problems with a new iPad2 64gb 3G. I am finding that when I am using an App it will suddenly drop out / crash and return me to the main menu screen. This can happen at any time, it may be after the App has been running for some time, for just a short time or before it has even finished loading up. It happens with all the Apps that I use including GarageBand, Mail etc and games Apps. It is not consistent and can happen even when the unit has be put down and is not being touched. It is not due to inadvertent touching of control switches.
It is starting to be really frustrating.