when i send a message on iMessage on my mac and i get a message back it automatically sends a message saying "Unknown command", i need help please help me.

Me too, with Mavericks...

I had the same problem on mavericks- I sent in a bug report- I'd fill one out too so this gets some attention from the engineers.

Its the same for me as well. Its so annoying but can't do much about it.

If there is anyway of getting "Messages" database refreshed for this. Do let me know.

Guys i got this from one of the post. Hope this helps it worked for me.

https://discussions.apple.com/thread/1809533

Same for me. I know it's originating from iMessage on my mid-2012 Macbook Pro, but how to stop it, I have no idea...

Go to iMessage Preferences >> General Tab >> AppleScript Handle at the bottom

Select None in the drop down and that should fix the issue for you. It worked for me that way.

I had this problem too. Thanks for the help.