Could not sign in to iMessage.

I had the same problem with iMessage' but not of the other people's causes - no hosts file weirdness, the logic board had not been replaced, and so on. I quit and restarted and logged out and in and rebooted and removed preferences file til my fingers were sore, no help. A clean (clean, mind you) re installation of snow leopard fixed it, and some other troubles.

(But not the SystemUIServer trouble. Sigh.)

Hi doughiedo,

If the Motherboard or Logic board has been replaced then you have to check the person that did this "flashed" the Serial Number back to the new board.

Open the Apple Icon menu top left and then About this Mac

In this Pane click twice on the item that lists the current OS version (it will change to the Build Number then the Serial Number)

8:53 PM Friday; April 19, 2013

 iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.3)
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb (Snow Leopard 10.6.8)
 Mac OS X (10.6.8),
 Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images."  No, Seriously

Nano wont allow me to clean up /etc/hosts ust says 'permission denied' PLEASE HELP

HI,

You have to be logged to the Mac in an Admin Account that has a Password that is not Blank.

If that is not the issue try

sudo vi /etc/hosts

8:40 PM Friday; May 31, 2013

 iMac 2.5Ghz 5i 2011 (Mountain Lion 10.8.3)
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb (Snow Leopard 10.6.8)
 Mac OS X (10.6.8),
 Couple of iPhones and an iPad
"Limit the Logs to the Bits above Binary Images."  No, Seriously

Perfect! That does the trick!

THIS ENDED UP BEING THE PROBLEM!

After tons of frustration and time being spent on this, this ended up being the issue. My logic board had been replaced by Apple a few months back, and they forgot to flash over the seriel number to the new logic board.

Recap of my issues:

• Could use iCloud for Photostream, Apple ID for iTunes
• Could not use same Apple ID for iMessage/Facetime... Error displayed: Check your network connection (while connected over Ethernet)
• iMessage was working properly on the same Apple ID on my iPhone and iPad
• Running OS X 10.8.4

Here's how you can check if this is the source of the problem for you:

1. Click on the Apple at the upper left of the screen
2. Click on "About this Mac"
3. Click "More Info"
4. Take a look at the "Serial Number"

After the repair, my serial number was "SerialNumber#"... clearly not a serial number, or the one that's written in my computer.

The solution? Just bring it into your local Apple Store Genius Bar

Just tell them that you need your serial number flashed over to the logic board. They'll confirm this by repeating the same steps above. Then they connect your computer over to one of their diagnostic ones via Ethernet. In 2 min, you'll be all set with a properly flashed logic board, and you iMessage/FaceTime will work just fine.

Hi - I struggled with this exact same problem for weeks. I suspect it popped up out of nowhere after installing Java or updating to 10.8.4 as I had not changed DNS or my host files or my router, or deleted any files deep in the system. Heck all I had been doing was reading PDF's and email and then all of a sudden Messages stopped working. Facetime too.

I struggled with the answers in this and other threads trying ALL of the fixes with no such luck. Then I resorted to a fix from my Windows days - I restarted my computer. Low and behold ANOTHER security update started installing. Upon reboot - messages and facetime WORKED. Sad but true, I had gotten so used to infrequent updates and rare reboots over the years that this simple fix killed my messaging ability for weeks.

BOTTOM LINE: 1. Install the latest Security Update 2013-003. 2 Reboot your mac.

Mine says i have a network connection, but my internet is working fine. What do should i do?.

Hi,

If you mean yours says it may be an Network issue it may be the app is not let through the Firewall

It may not be allowed through your router.

It would help to know the error messages precisely and what you have tried so far.

7:59 pm Sunday; January 26, 2014

 iMac 2.5Ghz 5i 2011 (Mavericks 10.9)
 G4/1GhzDual MDD (Leopard 10.5.8)
 MacBookPro 2Gb (Snow Leopard 10.6.8)
 Mac OS X (10.6.8),
 Couple of iPhones and an iPad