Default [SOLVED] Incall echo

I'm getting an issue with incall echo on both my and receiver side. Yesterday my Defy drowned a bit with unlocked battery cover, so it got some water inside... I think it was the time when it started echoing and now I have no idea where to start. Should I check HW or maybe flashing rom will help?

/edit: the reason was probably missing microphone gasket. It fell off when I disasembled my phone. Now it's on a right place and I'll test it tomorrow if it helped.

/edit2: solved. Defy adds echo when this yellow part is missing:
I <3 my girlfriend, I <3 my Defy.