[scoutinkeith]

are you sure that it's actuailly kicking out of OD?
how much do the RPM's jump?
I had a similar problem with my 99. wile cruising at a steady speed(cruise controle on or off didn't matter) the RPM would jump about 200 or so, then come back down. what my problem ended up being was the torque converter unlocking, then locking back(not actuaily coming out of OD).
turned out to be a bad TPS (Throttle Position Sensor). it had a bad spot in it, and was sending a bad signal to the computer, which was causing the converter to unlock.
you can test the TPS with a volt meter, and if it is bad, it only costs around $25, and you should be able to get it at most parts stores.
if you need directions on how to test you TPS, let me know and I'll post them here.