Mac Book Pro - Mac Mini; sharing stopped working after IP/Net change

Question

I apologize in advance for the length of this, I've got a complex issue that I've been unable to diagnose with the usual published notes...
I have a Mac Book Pro and Mac Mini. I previously had sharing and screen sharing working between both systems.
About a month ago I switched internet providers (to AT&T U-verse) and their router required me to make major changes to my internal network as listed below.
Since those changes the Mac Book Pro can not access the Mac Mini in any way via Finder options, but still shows it in Finder->Sharing. I can access the Mini via shell access (telnet/ssh, ftp, www) but nothing via the normal automatic Bonjour type accesses (file sharing, screen sharing).
Conversely, the Mac Mini has no difficulty accessing the Mac Book Pro in any way.
List of the significant changes that were made:
1) My main router was replaced by the AT&T router.
2) The AT&T router does not allow any fixed IP addresses within the network, requiring all of my network shemes to get re-done (I used a mix of fixed and DHCP previously).
3) The IP range changed for all computers due to the router.
4) Both Mac Mini and Mac Book Pro were and still are on DHCP.
5) The Mac Mini's wireless was disabled and it was plugged directly in to the Ethernet port on the main router.
The behavior of the system is as if the Mac Book Pro is locked on the old IP address (but only in the context of the Bonjour services). Although I can't prove this, there was a brief period where both the old and new router and ethernet and plugged connections were all active on the same network and during this period the Mac Book Pro accessed the Mini without difficulty (the old IP was bound to the wireless port on the Mini).
Unfortunately it wasn't until after I had exchanged this other router that I realized that things were not working correctly.
Another unusual clue, the Sharing used to say use afp://<mininame> to access from Windows and now it says afp://QVT_529. I have to assume this is something to do with the DHCP from the AT&T router but all of the AT&T system screens show the <mininame> properly bound to the active DHCP port and nothing hinting at what the QVT_529 references. Going to this address fails and I can't ping it from terminal.
I've been scouring the net for the last month trying different things with absolutely zero results on any front. All settings check out perfectly. No firewall changes were made. No evidence that anything is out of place.
However, I can still only connect in one direction. It just doesn't make sense.
Some things I don't know that I think might help me resolve the issue:
1) Any recommendations with how I might be able to get a better view of what Mac Book Pro might be trying to connect to via the Finder->Sharing link to the computer?
2) Any way to probe the Mac Mini's file or screen sharing features from the terminal (going around the Finder link)?
3) Any possible issues with local networks that might interfere with these services? (there are several switches/hubs between and other devices on the network, but everything checks out at the IP flow level)
Thanks in advance,
Barney

Answer 1

This is just a stab in the dark since I haven't run into this and I don't know all the steps you have taken (or researched.)
It seems to me that since it is working right from the mini->MB Pro, then the problem should reside on the mini's broadcast side or the mini's OSX firewall. If your firewall is set correctly (as you said), my guess would be that network or firewall preferences have been corrupted by combining multiple, conflicting settings for the same preference due to hardware changes. If I was experiencing this (assuming that every setting on the routers/switches and the firewalls (router/OSX) etc were 100% correct), I would create a new user account and verify that the problem is still manifesting itself. If this solves the problem, I know it is the user account that is messed up and not the OS. If this doesn't solve the problem, I turn off any sharing services, delete the resident Locations (by the drop-down menu in the Network System Preference) as well as the list of Connections (left pane of Network SP) and restart the machine. I then set-up new network, sharing services and firewall settings after the restart. This has solved all of my network sharing issues on my equipment, home and work. (Permissions not with-standing.) If this hasn't solved my problem, my next step would be to reset NVRAM, PRAM and clean system caches (using OnyX.) Reinstall of OSX commences then. I don't know enough of UNIX to be comfortable in terminal so if my steps above failed, I would be coming here to ask or, if I thought the problem resided on non-Apple hardware, the offending hardware support channels.
I don't know if this helps, but I hope so.
D.