Yes the tuner can pick up the analog channels however I never saw you list your area so I don't know if comcast has any analog in your area. If you plug in an old cable ready analog tv do you see any channels (you could try a digital tv that also supports ntsc but you may mistake some clear qam channels as analog) .
Comcast is one of the first to try and go all digital but it depends on the area, some have none, some have 2-13 (or 18), and some have 2-76 (or any other number up to 99)... I read recently that by April 1st they will be all digital nationwide and soon will also be encrypting the clear qam stations, including the locals so it would probably be best to get a cable card tuner. Right now I think the best deal is the SD HomeRun Prime with 3 tuners (I've seen some mistake the dual for the prime when ordering so be careful as that isn't cable card but does offer atsc tuning) as it can be got for $130 from amazon or newegg (I think this promotion ends tomorrow but its been around in the past)... A Hauppauge version of it that connects by USB rather than network with one less tuner is around $100 but I personally favor the ceton infinitv with 4 tuners.
I doubt this is your problem with the 1950 but my 5 or so year old hauppauge tuners (pvr-150, hvr-1600s, and a couple of others), recently lost their ability to tune my analog cable channels, I may get a snowy picture but usually nothing, tried new cable and checked if connections came loose, other computers, etc. However, the digital tuners (where applicable) in them still work as well as the analog rca or svid inputs, so I hooked up an old vcr to act as the analog tuner.