I'm having an iDrive problem also...although it just happened and not related to trunk washing. LOL!
Mine fluctuates between the grey BMW screen and then the "accept" screen, but it won't allow me to accept. The system will let me scroll/highlight accept, but doesn't recognize when i push the control down. I haven't tried unplugging anything, but the can't be too difficult, right? BTW, what is an ASK? YIKES....this car is just so damn expensive sometimes!!! Drives me NUTS! But I LOVE LOVE LOVE it!