Thank you for your reply, i tried swapping the channels but regardless of which channel i use it always locks one other out. With the MP limit i have no idea what is the limit on my dvr but when i unplug other 720p channels the one that is blocked out doesn't come back on.
Probably the best solution is to invest into a new dvr as the one i have was a rushed decision and very cheap when we moved houses last time.
Cheers