On Demand - Check back periodically?

I'm curious as to why many On Demand channels are not loading when I try to access them. When I chose a network it starts to load but never fully makes it and I get a message telling me to "Check back periodically for exciting new programing". So I check back periodically and still get the same message. These are networks that up until a week or so ago I could access. I can still access pay per view movies and a few networks. Is this a change in service or just a problem I'm having?