Hey I had the same problem roll into my shop last week and I could not duplicate the problem. I finally figured it out when the customer came to get his MDX. He was a little angry but when pulled out his keys I realized what his problem was... This guy had 3 huge rings on his hand a S*%# load of keys on his key ring the immbolizer system could not read the key. Acura says there should only be 1 key and a remote on the key ring. ?WHY? Notice when your starting the mdx if the green key symbol is flashing if it is remove the key and try again