what is this msg all about? on the home network there is one more computer.
(the ip shown on the attached pic is photoshoped for obvious reasons)

It means what it says.
Two devices with the same IP address, on the same network, cannot connect at the same time - each device must have a different address.
On a small home network, that's usually very easy to fix. If you have manually set the IP address, just change the last set of your IP to a different number. In your example, change your own IP address to 192.111.1.12
If you have your router set to supply DHCP addresses, this usually is not necessary, as the router won't give out the same address to two devices at the same time. Then you would make sure that each device is set up to accept the output of the DHCP server. That would fix it, too.

I dont know and i cant remember what the tech guy did, its been a long time! Where should i check and what do i need to change? Router specs or my macs?

Check in your Macs - System Preferences/Network pref pane.
Compare IP addresses on any Mac that you have. They should NOT be the same number.
Is the Configure drop down set for manual (or Static) IP? or for DHCP.

If you have changed setting recently, you should NOT compare another Mac to decide what settings to use, other than making sure that both are NOT set for the same IP address.
If you do find two Macs using the same manual IP address, then you can simply change one (add 1 to the last number), then click Apply. You won't need to restart or anything else, and you should be OK.

should i just let DCHP handle it? provided i have it on auto in all my computers

Sure - unless you have a reason not to use DHCP...

ok thanx