I hate to bump this, but I want to document a possible solution for the few others who had the misfortune to get this computer. On my last 4 rides, I reset the ride-specific numbers (TM, DST, AVS, MXS,,,) at the end of each ride, before the computer went to sleep, by setting MODE to TM and pressing the reset button until it cleared the data. That's worked for 3 straight rides, which is better than it ever did before.

Thanks also to DrIsotope who, in another thread, solved the problem of losing data because it was hard to get the sensor close enough to the magnet. First, he taught me that the magical thing was just a magnet (!), and second, he pointed out that small, powerful magnets could be substituted for the OEM ones. DrIsotope suggested Amazon as a source; I found 'em even cheaper (except for my time) at Home Depot. The sensor and magnet are about 5mm apart now, but I don't think I ever lose data.