why does file sharing with OS 10.8.3 fail only in one direction?

I'm having trouble getting file sharing to work in both directions.

I have a late 2012 Macmini and an early 2013 MBP, both running OS 10.8.3.

I can get my mini to connect to the MBP, access the public folders, and even share screen.

Going the other way from the MBP, the connection fails.

Taking cues from all the other discussions of the question, I have created an additional

administrator on the MBP and given him sharing only privileges on the mini. Booting in

Safe mode works fine on the MBP. And, I deleted preference lists related to sharing and security

on both machines.

I have verified both HDs, and repaired all permissions with Disk utility.

Although the name of the mini shows up in the sidebar of the MBP, neither admin user on the MBP

succeeds in connecting to the mini. It's always the same message - check the IP, etc.

I'm wondering if I can use Time Machine to back up the one "real" home folder on the MBP,

then completely rebuild the user list on the MBP, restore the home folder from TM, and clear things up that way.

I've been fooling with this since long before the 10.8.3 update. After that update, it frequently failed in either direction

until I started in on it again this morning and got the mini-to-MBP link to work.

Any help will be very greatly appreciated!!

Bob