|Check that you are watching the HD versions of the cable channels|
This is what I expected the cable guy to do. I don't think all of our cable channels are in HD. Many of them say HD, so they're obviously HD. I assume the ones that don't say HD are not HD, and they are the ones that are a bit blurry. Not sure what we can do to upgrade the viewing of those.
We've got another tech guy coming to take a look at it today, but I think we're stuck with some cable channels (CNN for example) being broadcast not in HD, and so on a screen this big it doesn't come out as great as we'd like.