Just heard from my DirecTV contacts and the problem has hopefully been fixed. Tivo engineers made some tweaks to the Advance Program Guide (APG) stream, so no software update is required. Note that you may experience one more reset until the new APG data fully downloads to your Tivo. Keeping my fingers crossed!
Sony SAT-T60 120GB (v3.5b)
HR20-700, HR20-100, HR21-200 HD DVR
HR10-250 HD DVR 400GB (v6.4a)
H21-200 HD Receiver
R10 DVR 160GB (v6.4a)