I tried all the methods here as well, no go. What finally worked for me was something different than what has been suggested from everyone else. It is rather simple to.
I tried FileNVRAM.dylib .2 and .3 .. I don't believe you actually even need these with the new Chimera on Mavericks. The problem exists on Apple's end in regards to registering your machine properly to imessage. after you reinstall several times it just gets confused it seems. I was popping up contact support and unable to activate with account errors for over 2 days of playing around.
What Worked (for me):
You need a real mac to do this, or at least a mac that can log into imessage successfully.
1. open imessage, then go to: Messages>Preferences>Accounts
2. click on your iMessage account (on left column)
3. on the right column select details (under sign out)
4. sign into your iMessage Account Details with your password and hit View Account.
5. re-enter your password and then re-enter it again to verify (you can use your same password)
6. hit save.
It appears this will reset your iMessage account information on apple's end and wipe out any devices that it may be confused with. The only bad thing is that you will need to re-enter your password on your "i" devices to log back into and register them with the iMessage service. not a big deal.
I run without FileNVRAM now and iMessage works fine. took me days to figure this trick out.
Let me know if this works for you, would be curious if this is the actual fix to the problem.