It happens once in a while with mine - doesn't take a few minutes to get it back on though. Only a couple extra pushes of the end button.
If you want to change the amount of time before the screen turns off, there's an app you can download here if you're registered...
http://mytreo.net/downloads/details-339.html?AlwaysOn
or send me an email and I'll send ya the app - ben AT netbilling.com