Hi Guys,
I have the same exact problem with my trany I guess for the past 2 weeks after reading your responses and comments.
I have 2000 X5 4.4 as original owner with little over 174,000 miles....and still clicking in full throttle...

However, today it was enough and I took my baby to a local BMW dealer to check this trany problem before the weekend.

First, after all diagnostics, I have been told by Tech, that I need my trany flush and that should take care the problem I am having, so I authorized the service.....but after all the work and testings, the same problem still remain without any changes ! At the end, Chief Tech came to me and he said that he needs to create a complete Service Claim file to send it to BMW North America for further investigation/assistance since this is their first case like this. I should hear from them within the week.

If someone is trying something different, keep us posted and I will do the same. Good luck.