I'm having the Live/Reason rewire looping problem too, but very predictably. The loop's audio quits after 5 repetitions, and enters again perfectly on the 7th. Every time.
12" Powerbook, 1Ghz, 768RAM, Panther, Reason 2.5, Live 3.01.
Looking forward to seeing the Ableton guys at NAMM Thursday!
N.