Xoutpost.com - TRANS FAIL SAFE PROG

I am have real live problems here and as you can imagine, support Is rather VERY limited.
My darling X5 (year 2000 / 4.4i) started having transmission failure some months ago. It came on intermittently and went off again a number of times. Managed until it failed a month ago. Initially though it was the gear switch position (item 5 24107512755 on link http://www.realoem.com/bmw/showparts.do?model=FB33&mospid=47746&btnr=24_0776& hg=24&fg=15) switch and got 2 replacements but the problem persist.
Yesterday, the transmission came back on. It keeps switching on and off every second and after the engine starts “hunting” (like the old year 1987 5 series), revving up and down continuously. It had done that 2 weeks ago and also some months back and then back to the fail safe mode.
Please help. Not fun driving around in high gear and cant change down.