2nd FOB was no different. Took car in a few days ago, and SA is advising they are having difficulty repeating the problem (not surprising, as leaving car alone a day would give me reprieve of the problem, only to return). I will say this, though: they loaned me an X3 3.0, and the acceleration is much better than my x5 4.8 in 2nd/3rd gear with the current problem.
Although I am educated in car repair, that was more of the old carburator type cars. I suspect, however, that there is a sensor in the transmission that is not functioning properly, or at best, intermittently.