Hey, i have the same Problem now and then (with the widgets).
Thats what i got recently:
Richard: Hi Daniel, thank you for contacting HTC Support. How may I help you today?
Daniel: Ok first a specific question: Do u know of problems concerning widgets on the homescreen having horizontal lines in them, kind of graphical errors
Daniel: I heard of different problems concerning that, so maybe u can tell me if it is a sofware or a hardware issue (So exchange phone or wait for hotfix)
Daniel: Oh and its the Sensation
Richard: I have not heard of this issue before. It sounds like a graphics driver problem. I would advise you to factory reset the phone. If the problem is still there then it will be a hardware fault.
I will test that somewhen, at the moment I am too lazy to backup all of my data...