Why does my cable work properly with one TV, but not another?

My gf moved into an apartment last summer with cable included in the rent. The landlady said that she had all the channels, but only about a dozen channels seemed to work with her brand new LG LCD television (30 inches or so). If we plug in other numbers manually, we only get static. We kind of figured that a digital cable box would be necessary to get the rest of the channels (digital cable is pretty much par for the course in our area), but we don't watch enough TV to have bothered with it.

When I moved in, I brought my 40 inch Samsung LCD television, also purchased new last summer, and we moved her TV into the bedroom. Her TV still gets the same dozen channels, yet mine can receive the whole spectrum of regular cable channels (i.e. a hundred or so). My TV connects directly to the same cable jack that hers was with before, and doesn't go through any other ancillary devices to get there.

So the question is, What gives? Why, with two relatively new LCD televisions, does mine receive all the channels we're supposed to get, while hers doesn't?