Seriously, one of you reading this must understand this crap. I asked this before and got crickets. I emailed email@example.com (the folks I bought the new pre-installed drive from) and they never wrote back.
The web page on the Tivo for a recorded show has links for "view", "tmf", "ty" and "asx". Before the upgrade, the "ty" link would give me a downloadable file, but now it gives me a 404.
I assume that there's some piece of support software missing that existed on my old drive but that doesn't exist in their new build, but I can't figure out what. I've upgraded TivoWebPlus to 2.1.b3, and I've installed mfs-utils_bin.mips-20050604.tar.bz2 into /var/hack/mfs_ftp/, and that didn't seem to do it. I can't make heads or tails out of what's actually going on in /ptvupgrade/TivoWebPlus/modules/extract.itcl. I don't see anything in the log files, either, though it looks like it should have logged something. The .asx links do work, so it's getting at least that far. (They return a small XML file pointing at a "tivo:" protocol URL.)
Answers that go "don't use .ty files, use the Home Media Option" are no good because HMO is not supported on DirecTivo.