I have spent hours attempting to solve the same issue - in fact the same issue as I have my son's hockey on a DVR recording from a HDTV broadcast.
What was most frustrating is on my Motorola DVR there are USB and 2 firewire outputs, which one can use to transfer download to an HD camcorder, which I attempted in this case. Unfortunately, it was only have screwing around for hours unsuccessfully did I find out from my cable provider (also the DVR retailer) that the USB and firewire outputs are disabled on the units they issue.
I have been unable to source anything to address the issue. Looks like an answer is on the way from Hauppauge with their proposed HD PVR, scheduled for delivery May 1 (???). No price info, but suspect it will not be cheap.
http://www.hauppauge.com/site/products/hd_pvr.html