I've been working on this issue for 3 days now and this morning I made things even worse and I'm hoping someone can help me out.
I have an AT&T Samsung Galaxy S2 (SGH-I777) (The splash screen says GT-I9100 on the only firmware I can get to load)
I am currently running the CyanogenMod 9 Resurrection Edition (cm-9-20120420-ODIN-galaxys2.tar) but I have no audio on any phone calls. I can place outbound calls and they connect, but neither end hears anything.
I tried fixing this today by going back to stock firmware using Odin, but I accidentally put the *.tar file in the Bootloader location and hit start. It completed like it worked, the phone rebooted and it displayed the AT&T splash screen, but then just stayed on that screen and never booted.
I was able to go back to the CyanogenMod 9 Resurrection Edition, and I even tried MIUI and both boot up, but the phone doesn't work in either of them.
I'm hoping someone has an idea because I'm running out of things to try.