Is your Macbook Pro client you using Mac OS X Lion (or Mountain Lion as this is the Mountain Lion forum) Screen Sharing client or are you using RealVNC client?
On the destination Macbook are you using System Preferences -> Sharing -> Screen Sharing? (preferred)
Or are you using System Preferences -> Sharing -> Remote management? (ONLY if you are controlling a room full of Macs, such as a classroom or office environment).
Or are you using the RealVNC Server?
If using System Preferences -> Sharing -> Screen Sharing, what is "Allow access for:" set to? "All users" or a select subset of users?
If connecting using the Macbook Pro Mac OS X Screen Sharing client to the Macbook Mac OS X Screen Sharing server, are you specifying the username and password of an allowed Macbook account?
Or are you trying to use the VNC password as specified by the Screen Sharing -> Computer Settings... -> VNC viewers may control screen with password: xxxxx
Wow, I was sure I was posting under Lion (not ML Server), so I have no idea how this ended up in MLS.
To your questions, and there are many, some of which I am not sure how to answer.
I am using Lion 10.7.5 on the MB and MBP, and Leopard on the PowerBook 12".
The procedure I used to access the MB server function on my home network consisting of these three laptops (connected with an Airport Extreme) was the same for the MBP with Lion 10.7.5 and PowerBook with Leopard 10.5.8.
Just to give the details of the Screen Sharing, I enabled this function on the MB with all users enabled, then on the clients (MBP and PB) went to Go>Connect to Server, then put in the local MB address.
The PB connected and for the MBP nothing happened.
No time now to go into description of RealVNC access, but I used an identical procedure to connect PB to MB, as I dod for the MBP to MB connection, again with same results.
So my basic question is, why does the old PPC 10.5.8 connect to an Intel 10.7.5, but not the Intel 10.7.5 to another Intel 10.7.5 using the identical procedure?
Do you get errors? If so what are they.
In the past, I have had issues Leopard, such that I needed to clear out my Kerberos credentials from an Applications -> Utilities -> Terminal session
I did this on both client and server.
I'm not saying this is your problem. Just mentioning something that has happened to me in the past.
it would be good to get any error messages, dialogs you see.
The message that appears on the MBP with Lion is:
"Connection failed to [local address]
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 your network connection is working properly."
Again, same method using a PB with Leopard works flawlessly using the same local address and I am looking at and controlling the MB with Lion w/o problems.
This thought just occurred to me. Do you have the Macbook Pro Firewall enabled? System Preferences -> Security & Privacy -> Firewall. Is it enabled? If it is, try disabling it.
Time to ask a question about your network setup. Wild Goose Chase questions.
You mentioned an Airport Extreme. Is that the ONLY router in the house? The reason I ask, is that if you have multiple WiFi routers (for example because your house is so large, you need more than one WiFi router to cover the entire house, or your house has has 4 floors you need to cover and the structure interferes betwen the basement to the converted attic), you could have multiple subnets which could affect the ability to connect to devices on the other subnet. If you do have multiple subnets, there are ways to address this.
I would like you to download and run "Bonjour Browser"
Run Bonjour Browser on the Macbook Pro (and any other Macs you like). I want you to look for "Remote Frame Buffer" entries (VNC Servers - aka Screen Sharing servers). Click the triangle to show all the systems offering VNC server.
Assuming you see your Macbook listed, click on its triangle to show the IP address and port number. It should be something like 10.0.1.nn:5900. Hopefully you see the same IP address as you think your Macbook has assigned to it (which you can see via Macbook -> System Preferences -> Network -> Advanced -> TCP/IP.
If you are not seeing your Macbook via Bonjour Browser from your Macbook Pro, then there is something affecting your ablity to see the Macbook.
If you Mac stays at home, then Stealth mode is meaningless.
On the road, Stealth mode means you Mac will not respond to queues on unopened ports. Normally a query on an unopened port would get a Negative Acknowledgement, which would tell the query a system was at this address and maybe worth investigating further.
But generally speaking if you have good passwords on any Sharing services you are offering, it is unlikely someone will break into your Mac.
If having the Firewall services active when you are on the road, you might want to look at ControlPlane
<https://www.controlplaneapp.com> that claims to dynamically switch many of your settings based on where you are, so at home you could have Firewall off, and out of the house, have it on.
I'm glad you found the problem.
So, suddenly it stopped working.
Complete mystery to me.
I did a few things that you suggested, such as downloading the Bonjour Browser, seeing the device I want to access as Remote Frame Buffer, checking all IP addresses to make sure they match.
In the Finder window I see the device I want to access under "Shared", but when highlighting it I get a "Not connected" message in the top of the Finder window. Using my PowerBook I get "Connected as: VNC" in the same location, and the PowerBook connects to the newer devices without issue.
I'm down to very wild guesses now
By any chance do you have a neighbor with an unprotected WiFi network? What I'm thinking is maybe your Macbook Pro is connecting to the neighbor's network instead of yours.
This actually happened to me once, so it is not totally far fetched. Then again, most likely not the problem either.
You could try turning off WiFi, then turning it back on again.
Have you tried plugging in an ethernet cable just to see if it is the WiFi vs networking in general vs just Screen Sharing.
You could try a reboot? I almost never suggest this, but when desperate...
Again, I'm just throwing suggestions at the wall, but I'm not very confident anything will stick.
The problem was Intego VirusBarrier. All three (MB, PB and MBP) have Intego istalled with the same settings.
Turns out, the MacBook identified the MBP as an intruder and blocked the local address of the MBP. It did not do the same with the PB and allowed access.
Changing the MBP local address to a trused one from a blocked one solved the problem.