It might be an account issue like mine was. Something went wrong on their end of things in my case. They first checked the signal and changed the box, but neither fixed the issue. The fix was for them to reset my account on their computers.
What kind of box are you experiencing this on? Mousetamer make a very good suggestion here, and says to have your account checked into..
I however have also experienced this issue, but it was using my older 3250HD box. The kids would constantly go to Treehouse On Demand, and although it would load, there would be no menu's or options to choose a program.
I heard from an insider once that this perticular box (3250HD) would have problems as it did not have "enough" memory to support the newest features that Rogers was using, and I chaulked this problem up to that - Not enough memory in my box. I could fix the issue by rebooting the box, but since you say you did that and it still didn't fix the problem, I would look into a box swap, or an account problem at this point... also could be bad signal/RF. Wouldn't hurt to have a tech come by and check everything out for you.... if he determines its a box issue, he should have a replacement on board (providing box is a rental and CAN be swapped) and will swap it out for you.