Did you make sure only your Xbox Live profile you are playing SC with is logged in to the Xbox? No other guest profiles or similar? In that case, there is something in your profile causing it to not show CaS. I seem to remember someone saying voicechat settings could matter, maybe try muting/unmuting voice in headset or speakers in the Xbox settings?
Btw, when you have the problem of not seeing other peoples CaS, can you then see their playing cards, or are they just gray? Can you write in the text chat in player rooms?