Ah... don't feel bad, I did the same thing a while back... what a nightmare!!! I tried so many things, I am going to be honest with I am not sure exactly what actually works, but if I remember correctly, I changed the host name to something else, then waited a day or so and then changed it back.
I believe I also had to go through and rebuild each and every domain that I had installed!
Not good times, wish I could forget that little episode! But on the bright side, once I got the server all ironed out, my server is just working beautifully now, email server is perfect, and websites are crazy fast.