Screen Sharing/network problem seems confined to 1 volume. What's the fix?

Question

I am having a networking problem on one of the volumes of my multi-volumed, three-Mac local area network, and I need a networking guru to identify the specific software file(s), application(s), or system configuration that is the cause of the problem. I have already spent several hours checking and re-checking the various hardware and system preference settings involved, and I have narrowed the problem down to a software corruption issue and/or system configuration issue on one volume.
I now need someone to identify specifically what the nature of the problem is, and how to eliminate it. I am not looking for a sledgehammer solution that says I should re-install all of the Mac OS X software on the problem volume. That may be held in reserve as a last resort. I'm looking for a more elegant approach, one that points out the specific corrupt files to remove without disturbing everything else.
Here's some background to set the context. I have a MacBook Pro laptop; a PowerMac iMac G5; and a PowerMac G4 hooked up in a network. All are running Leopard 10.5.8. All have file sharing and screen sharing enabled. Besides being able to connect to each other using registered users, my goal here is for each of the Macs to be able to share the screen of the others upon my demand. Since each of the 3 Macs can theoretically share the screens of the other 2, that makes a total of six possible connections. Five succeed; one does not. That's the problem. I am trying to determine why the iMac G5 cannot share the screen of the MacBook Pro.
The iMac G5 has no problem sharing the screen of the PowerMac G4. That connection is fast and immediate. But, every time that I hit the Share Screen button on the iMac G5 to try to connect to the MacBook Pro, I get a window with the blue barber pole spinning for two or three minutes as it is allegedly "Connecting to Mac Book Pro," followed by a window with a headline telling me that "Connection Failed to MacBook Pro." The text within that window goes on to say: "Please make sure that Screen Sharing (in the Sharing section of System Preferences) is enabled on the computer to which you are attempting to connect. Also make sure that your network connection is working properly."
Well, as I indicated, the PowerMac G4 has no problem sharing the screen of the MacBook Pro, so the Screen Sharing settings on the laptop are correct; and the iMac G5 can share the screen of the PowerMac G4, so its network connection is working properly in that regard. It is only in regards to sharing the screen of the MacBook Pro that the iMac G5 is not working properly.
The reason why I say that the issue must be unique to the one volume in question, let's call it "iMacG5 Music," is that another Leopard volume on the same computer has no problem whatsoever in sharing the screen of the MacBook Pro. Whenever I boot up in that volume, let's call it "iMacG5 JMB," it makes a network connection with a registered user name immediately, and it is able to share the screen of the MacBook Pro within a second of my issuing the command. In sharp contrast to the success of the iMacG5 JMB volume, the iMacG5 Music is unacceptably slow (several minutes slow!) in making a network connection with the MacBook Pro, and it always fails to share the screen of the MacBook Pro, preferring instead to take about three minutes to attempt the connection, before announcing its failure.
Since the iMacG5 Music volume makes an immediate network connection to the PowerMac G4, as well as sharing the screen of the PowerMac G4 the moment I ask it to, I have concluded that the hardware of the iMac G5 is just fine. The problem seems confined to the system software and/or associated networking files that are unique to the iMacG5 Music volume. I just don't know what those files could be, or where the problem lies, so I've issued this call for help.
Let me add one more little twist to this puzzle which baffles me even more. I use external LaCie Firewire drives as clone backups of my Macs. As part of my trouble-shooting process, I booted up from the cloned versions of the iMacG5 JMB volume and the iMacG5 Music volume. What I learned surprised me!
The iMacG5 JMB clone worked just fine in making a fast network connection to the MacBook Pro, as well as sharing the screen of the MacBook Pro. I expected that. What I did not expect was that the iMacG5 Music clone was also able to make a fast network to the MacBook Pro, as well as share its screen!
Yes, that's right. It's weird! Screen sharing works OK when I start-up from the clone of the iMacG5 Music volume, but it does not succeed when I boot up on the source itself! I was surprised to find that out, but I'm glad I did.
(Over the past few days since I executed the last clone, I did use Drive Genius to de-frag the source volume, and maybe that has contributed to the problem I am now encountering. But it's hard to say, since nothing else seems to be amiss.)
One solution, I suppose, would be to sync the clone back to the source. But, before I do that, I'm just wondering if anyone has a clue as to the nature of this problem on the source volume and what I might do to remedy it—short of re-installing the system software or restoring from the clone. Anyone have any insight to this problem?

Answer 1

CORRECTION #2:
Ignore the previous "CORRECTION" post.
Oops, excuse me, I wrote that sentence correctly the first time.
I was trying to point out that the ability of the iMac G5 computer to connect quickly and effectively to the PowerMac G4 when booted up into the iMacG5 Music volume was an indication (to me, anyway) that there is nothing wrong with the computer's hardware, nor its network connection ability, but that the problem lay somewhere in the files/settings used to connect to the MacBook Pro, which it cannot accomplish.
This is what happens when I get engrossed in one of these technical morasses and it ***** me into its vortex all through the night... time for bed.