It actually makes buying a nav computer much easier. If you look on the bottom area of the part number label, you will see the hardware and software versions of the MKIV in the format "HW: 1.01 / SW: x.x". The part number of the MKIV is tied to the original OS loaded on the computer, as indicated by the SW number. Almost every one I have ever seen has HW 1.01, so I do not think that there were different versions of the HW more prone to issues.

Here are a couple posts with known good MKIV part numbers. If you buy a MKIV from this part number list, you will be fine. They are all equal. Just make sure that you do not get a mis-identified NAVI02 or NAVI03 from a new body style 7 Series.

http://www.bimmerboard.com/forums/posts/217370
http://www.bimmerboard.com/forums/posts/445620/
http://www.bimmerboard.com/forums/posts/267776/
http://www.bimmerboard.com/members/j...er%20Guide.pdf

__________________
SOLD
2000 E38 750iL Highline Edition, Upgraded with the lastest 2006 X5 Electronics
MKIV Navigation, 16:9 Display, Bluetooth, TV/Video with Backup Camera, Sirius, and Aux Input