I sent an email to customer support and received the solutions below. Thanks for a very cool device.
Do your channels have names entered for them in HDHomeRun Setup? QuickTV will report a channel scan is needed if it isn't able to parse any channels, which at a minimum requires having a name entered.
Regarding the HD channels freezing, while you have a channel playing, check the system tray and hidden icons areas for an icon labeled VobSub or DirectVobSub. Double click on it, and locate the Loading option (it may be on the Main tab or some other tab depending on the exact version installed. Set to Do not load. Click OK. This program is basically designed to insert itself between the video decoder and video card. In modern configurations where the video card is decoding the video, it breaks playback.