Hm, my old player (MkII, 18GB, 1.03) has not frozen once in more than a year of more or less 24 hr/day playing (car, work, home, and I often fall asleep with it playing), and I think this is the general experience. In other words, something might be wrong with your hardware. Apart from memory test, though, I don't know what to do....
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Dragi "Bonzi" Raos Q#5196 MkII #080000376, 18GB green MkIIa #040103247, 60GB blue