Wirelessly posted (HTC Diamond: Mozilla/4.0 (compatible; MSIE 6.0; Windows CE; IEMobile 7.11) Sprint MP6950SP)
I suggest using an app that will show which processes are running and how much memory/cpu is being used at any given time. That will show you what is going on.
I suggest downloading ClearTemp if you haven't already. This app provides a link to show running tasks and processes plus it mainly will allow you to free up wasted storage memory by clearing temporary files. If you run it at least once a week it really helps to clean up things and will help your device run better.
You can find it at www.mobisapienz.com