I just spent most of the day with the same problem. The short answer is no, it does not matter that the DCT700 says "IR blast = No".
The fix defies all logic:
1) None of the Motorola IR codes work. I ended up using the GI Code 00093-Medium
2) It worked intermittently for about a half hour, then stopped working at all.
3) I called Tivo support, not much help, but the rep asked me to view the IR blasters through my video camera so I could see if they were sending anything or not (you'll supposedly see a red flash, I didn't see anything).
4) But, when I picked up the IR blasters, pointed them towards the camera and changed the channel on the remote, the channel actually changed on the Tivo.
5) Now, my IR blaster does not work if its near the cable box. I have both of them hanging down about 3 feet under my Tivo, and its changing channels fine.