I've been having the same "dynamic drive inactive" error on my iDrive for a while took it to the dealer they said I need a new ASR/ARS module. My battery also needed changing so I did and its been 2 weeks without error on iDrive however I just scanned the car for errors a few hours ago and it does show up in INPA. I will clear it out tomorrow and see if it comes back in INPA though. But all in all after changing the battery the error stop popping up in the iDrive screen.
85 Honda Accord(Sold), 93 Lexus GS 300(Gave to lil Bro), 96 Lexus LS 400(Sold) 03 BMW 525i(Traded/Sold), 09 BMW 750Li, 07 BMW 530i, 04 Pontiac Grand AM (Daily Driver), 08 Ford Focus (Wife's Daily Driver)