In trying to be helpful let me post my information as well. This is the log file I get. The "cause" of iMessage not working is peculiar. Literally it crashed with an error around 9am this morning and hasn't worked since. I keep getting the "The server encountered an error processing registration. Please try again later".
I have tried at both home and work. I have tried adding the public dns server 8.8.8.8 to no avail. I have flushed the cache several times. I have deleted all the keys with the name "message or messages" from the keychain access, I have deleted all ichat and imessage and com.apple.whatnot from the ~/Library/Preferenes file. I tried creating a test account and signing in. I have also tried deleting all my "accounts" from the computer and signing in that way. My wifes account does NOT work on this computer.
I HAVE successfully logged into my account on my wifes MBP.
Peculiar is that I keep seeing an error in the log saying "netbiosd: name servers down?" as if dns lookup is having an issue. I should note, I have a hackintosh HP Probook 4530s. The reason I mention that is, I do not think this is a serial issue. I have been using this for six months, with iMessage with no issue. It just quit working while I was at work. Something is up.
Anywho, maybe my problem is different, but here is my log file.
1/2/13 3:57:08.442 PM Messages[377]: [Warning] Empty account query with service: iMessage
1/2/13 3:57:08.748 PM com.apple.SecurityServer[24]: Session 100016 created
1/2/13 3:57:20.682 PM imagent[202]: [Warning] *** Listener ID: com.apple.CalendarAgent does not have capability: (Status), not allowing request
1/2/13 3:57:20.682 PM imagent[202]: [Warning] 1 IMFoundation 0x000000010c3cfbe2 IMLogBacktraceToDepth + 69
1/2/13 3:57:20.683 PM imagent[202]: [Warning] 2 imagent 0x000000010c380de8 imagent + 81384
1/2/13 3:57:20.683 PM imagent[202]: [Warning] 3 imagent 0x000000010c381f6a imagent + 85866
1/2/13 3:57:20.683 PM imagent[202]: [Warning] 4 CoreFoundation 0x000000010cf7663c __invoking___ + 140
1/2/13 3:57:20.683 PM imagent[202]: [Warning] 5 CoreFoundation 0x000000010cf764d7 -[NSInvocation invoke] + 263
1/2/13 3:57:20.683 PM imagent[202]: [Warning] 6 CoreFoundation 0x000000010cf766a9 -[NSInvocation invokeWithTarget:] + 57
1/2/13 3:57:20.683 PM imagent[202]: [Warning] 7 IMFoundation 0x000000010c3cc5d5 im_local_object_peer_event_handler + 7128
1/2/13 3:57:20.683 PM imagent[202]: [Warning] 8 IMFoundation 0x000000010c3cc6b3 im_local_object_peer_event_handler + 7350
1/2/13 3:57:20.683 PM imagent[202]: [Warning] 9 IMFoundation 0x000000010c3cc767 im_local_object_peer_event_handler + 7530
1/2/13 3:57:20.683 PM imagent[202]: [Warning] 10 Foundation 0x000000010c8bc677 __NSThreadPerformPerform + 225
1/2/13 3:57:20.684 PM imagent[202]: [Warning] 11 CoreFoundation 0x000000010cf02101 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
1/2/13 3:57:20.684 PM imagent[202]: [Warning] 12 CoreFoundation 0x000000010cf01aed __CFRunLoopDoSources0 + 445
1/2/13 3:57:20.684 PM imagent[202]: [Warning] 13 CoreFoundation 0x000000010cf24dc5 __CFRunLoopRun + 789
1/2/13 3:57:20.684 PM imagent[202]: [Warning] 14 CoreFoundation 0x000000010cf246b2 CFRunLoopRunSpecific + 290
1/2/13 3:57:20.684 PM imagent[202]: [Warning] 15 Foundation 0x000000010c8c489e -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 268
1/2/13 3:57:20.684 PM imagent[202]: [Warning] 16 Foundation 0x000000010c85d18a -[NSRunLoop(NSRunLoop) run] + 74
1/2/13 3:57:20.684 PM imagent[202]: [Warning] 17 imagent 0x000000010c3750ab imagent + 32939
1/2/13 3:57:20.685 PM imagent[202]: [Warning] 18 libdyld.dylib 0x000000010ea937e1 start + 0
1/2/13 3:57:20.685 PM imagent[202]: [Warning] *** Listener ID: com.apple.systempreferences does not have capability: (Status), not allowing request
1/2/13 3:57:20.685 PM imagent[202]: [Warning] 1 IMFoundation 0x000000010c3cfbe2 IMLogBacktraceToDepth + 69
1/2/13 3:57:20.686 PM imagent[202]: [Warning] 2 imagent 0x000000010c380de8 imagent + 81384
1/2/13 3:57:20.686 PM imagent[202]: [Warning] 3 imagent 0x000000010c381f6a imagent + 85866
1/2/13 3:57:20.686 PM imagent[202]: [Warning] 4 CoreFoundation 0x000000010cf7663c __invoking___ + 140
1/2/13 3:57:20.686 PM imagent[202]: [Warning] 5 CoreFoundation 0x000000010cf764d7 -[NSInvocation invoke] + 263
1/2/13 3:57:20.686 PM imagent[202]: [Warning] 6 CoreFoundation 0x000000010cf766a9 -[NSInvocation invokeWithTarget:] + 57
1/2/13 3:57:20.686 PM imagent[202]: [Warning] 7 IMFoundation 0x000000010c3cc5d5 im_local_object_peer_event_handler + 7128
1/2/13 3:57:20.686 PM imagent[202]: [Warning] 8 IMFoundation 0x000000010c3cc6b3 im_local_object_peer_event_handler + 7350
1/2/13 3:57:20.687 PM imagent[202]: [Warning] 9 IMFoundation 0x000000010c3cc767 im_local_object_peer_event_handler + 7530
1/2/13 3:57:20.687 PM imagent[202]: [Warning] 10 Foundation 0x000000010c8bc677 __NSThreadPerformPerform + 225
1/2/13 3:57:20.687 PM imagent[202]: [Warning] 11 CoreFoundation 0x000000010cf02101 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 17
1/2/13 3:57:20.687 PM imagent[202]: [Warning] 12 CoreFoundation 0x000000010cf01aed __CFRunLoopDoSources0 + 445
1/2/13 3:57:20.687 PM imagent[202]: [Warning] 13 CoreFoundation 0x000000010cf24dc5 __CFRunLoopRun + 789
1/2/13 3:57:20.687 PM imagent[202]: [Warning] 14 CoreFoundation 0x000000010cf246b2 CFRunLoopRunSpecific + 290
1/2/13 3:57:20.687 PM imagent[202]: [Warning] 15 Foundation 0x000000010c8c489e -[NSRunLoop(NSRunLoop) runMode:beforeDate:] + 268
1/2/13 3:57:20.688 PM imagent[202]: [Warning] 16 Foundation 0x000000010c85d18a -[NSRunLoop(NSRunLoop) run] + 74
1/2/13 3:57:20.688 PM imagent[202]: [Warning] 17 imagent 0x000000010c3750ab imagent + 32939
1/2/13 3:57:20.688 PM imagent[202]: [Warning] 18 libdyld.dylib 0x000000010ea937e1 start + 0