Are you saying that you got rid of the issue by NOT using the middle name field? I've got one user with this issue and so far I have not figured out how to fix it. I've turned off all syncing, as I thought it had something to do with Mobile Me or our
I've also got a similar problem with the medical suffix on the contacts for my parent's names. I keep putting them in as <First as first name> <Last as last name> <D.O. as suffix>, and they end up as <First as first name> <"Last D." as middle name> <O. as last name> <nothing in the suffix field>. I thought this was caused by my Gmail syncing, but I'm not sure now.
If you want to add a middle name field (or others) to a record in Address Book:
have a contact selected that you are currently editing
click Card --> Add Field --> Middle Name
We're definitely seeing this in 10.6.8, I may be seeing the suffix issue in 10.7.2.