If you're using a Dynex 720p TV, you shouldn't be setting the resolution of your PC any higher than 1280x720. It sounds like you've got the resolution set to 1360x768. I think you'll find that setting the screen resolution to 1280x720 will allow you to re-enable HDMI Link without issue. If I'm not mistaken, HDMI Link Assurance attempts to confirm that your display is outputting the resolution that your graphics processor is sending correctly. If you're sending the TV a higher resolution than it can display, at best it's going to use some basic processing on its end to stretch or scale it down to fit. Even if it looks fine, this will at minimum introduce latency, which may not be noticeable in video but can really affect gaming if that's a part of your media diet.
Also, and I'm not sure about this, but HDMI Link Assurance may be necessary for displaying HDCP content. Primarily, that would affect playing back encrypted blu-ray disc videos (such as retail blu-ray movies), as one might do with Cyberlink PowerDVD.