THIS! My cable card install with Time Warner was a nightmare. No one knew anything at all about Cable Cards, the techs who installed the cable card were clueless but yet TWC required a visit to plug it into the back of the Tivo (they refused to let me install it myself), but then had no idea how to activate it, and neither did any of the tech support people. And it took 4 calls to figure out that I needed a Tuning Adapter as well.
Only when I did enough Googling to find their Tier 3 Cable Card only tech support phone number on a Tivo forum did everything finally start working. It only took about 30 seconds once I got the right people on the phone.
It's actually against FCC rules to make it so incredibly difficult to use a CableCard, so I ended up writing up a complaint to them, and then TWC got really nice to me and gave me a few months of free cable. And at least I haven't had any issues since.