A few weeks ago, a bought a new Philips 27" tube TV from Walmart. My wife and I don't have cable, so we were relying on the digital signals the local TV stations are sending out to get a much clearer reception. And indeed, the local channels are clear as a bell when switching from the analog signal to digital. However, after watching for a few minutes, the image becomes pixelated and blocky and often freezes up. I'm trying to rule out a bad TV by thinking that if it picks up the signal at all, then I'm cool. I'm hoping it's just the signal itself that isn't quite up to par yet. I could be wrong though. Is this an issue with my TV or the signal? Any recommendations? Thanks!