said by yyzlhr:pretty funny since this guy works for the cable company he should know what he is talking a bout
To the OP, it sounds like you have a whole home PVR setup. If so they filter they installed is necessary to prevent the signals related to the Whole Home PVR network from leaking back into the cable plant. If the filter is not installed it can potentially cause problems like you described and can interfere with your neighbours as well.
I don't know if comcast utilizes SDV, but the problems you described with tuning into the premium channels sounds like an SDV issue. With SDV, your set top box must communicate with the head end to request the channel you want. If you have low signal the box may have trouble communicating, hence the delay in tuning into certain channels. Most STBs have a diagnostic screen you can access where you should be able to read the signal levels.