What could it be? Receiver failing/ bad cable/ bad LNB/ poorly aimed dish/bad connectors, lets see what else can I guess at? The only information you have provided is a 512 DVR and 3 channel numbers.
Sounds like a software glitch. By the way, red means you do not subscribe, green means you do not subscribe but can order the channel if your receiver is connected to either phone or dsl. I wouldn't worry about it.