Hey Sabu, I've figured it out, and it's similar to, but not exactly the same as what you did.
I have a VSTs folder where I put all my VSTs. So, when I first installed Sonar, I installed the all the VSTs in my custom folder. From there, Sonar and Ableton Live were both able to recognize all the VSTs that came with Sonar 7. But I was doing some folder managing/maintennance on my system, and I moved all the VSTs to a different location. Sonar and Live were both able to rescan the VSTs from that location, except for SessionDrummer2.
I moved SD2 back to the original location in which I had installed it into, and now both programs are able to scan and recognize SD2. This is the only VST which has this problem. So for me, it didn't have to be under the Cakewalk program folder, but it needed to be in the exact location that it was originally installed in, or else the programs couldn't scan it.