Wirelessly posted (HTC Diamond: Mozilla/4.0 (compatible; MSIE 6.0; Windows CE; IEMobile 7.11) Sprint MP6950SP)
I don't think you can keep the screen from turning on completely but you can certainly change the amount of time it stays on. You can change this in your devices backlight/power settings. Set it to turn off after say 10 seconds. S2U2 could be overrideing your power/backlight settings so check that and see if you can set it differently. S2U2 itself could be draining your battery.
Also, in sounds and notifications uncheck the box that says show message on screen for your text message notification.
Hope something there helps!