Well that was happening to all miui roms I tried. If u move dalvik cache on SD you have this problem.
The solution is simple.after you move dalvik cache on sd you enter again on recovery mode and you re-wipe cache and dalvik cache.after that sound will work fine
Sent from my Nexus One using the miui-dev.com Forums App
Cleaning cache worked for me for now. Isn't the audio volume handled by the kernel? Maybe changing to a different one could prevent the problem from reappearing, does anyone know kernels that can be used with MIUI?