I was facing the same problem, but now I found a workaround. Tell me if it works for you too.
The thing is, you have to have your contacts' full phone number, so for instance, I'm no Brazil and just having a number such as 5550-1111 wouldn't work; only after adding country and city code did Messages start working with devices I know to have support for iMessages (iOS5).
In the end it means that a contact whose number is something like +55 (11) 5550-1111 works (and it also means I'll have to update all my contacts to be able to use Messages with them).
Hopefully this isn't too confusing.
I am also getting the same user-not-available errors as well as many others. I cannot find a pattern or make sense of the error messages. I've tried all the phone number configurations.
A couple of other interesting points include
- I also got errors the first day saying a user (recipient of my message) was not configured to receive messages. The next day that person was no longer colored in red and did indeed receive my message. They were oblivious to what I was trying to do and subsequently assured me that they had not made any sort of account or configuration changes in those 24 hours.
- I've gotten messages saying that recipients were unavailable because they were offline (while I saw them online in my Gmail chat list)
- I had no trouble sending to my mother-in-law, who never turns on the new iPhone we bought her for Christmas
- Anybody else seeing a grayed-out message on the text line saying that Bonjour is offline?
Is there any documentation anywhere on how to use this service?
To my son on his 4GS using his number or his Apple ID (He has both set on his Phone)
Replies to my Apple ID also show.sync on my 3GS
Please, if posting Logs, do not post any Log info after the line "Binary Images for iChat"
iMac 2.5Ghz 5i 2011 (Lion 10.7.3)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
"Limit the Logs to the Bits above Binary Images." No, Seriously