Could a firmware update to 1.6 break the mic + ear-speaker?

no its not 1.6
it could have been firmware
more likely the headset glitch where you need to insert and remove the headset in rapid succession to free the dirt and short in the jack that causes the device to be stuck in headset mode.
there are posts about it.
its more likely the repair center flashed it, cleaned it and it worked but its likely the cleaning was the fix

 

I cannot believe it hehe, the exactly same thing happened to me, but for a different reason.
On a random sunny day my mic and ear-speaker went dead. Also the normal music playing speaker went dead. I had jc6 installed at the time so i went back to ik5 but it didn't help, next i tried ii5 and it still didnt work.
So i left the ii5 on the phone and took it for repairs under guarantee.
The funny thing was that the guy at the repair shop had the same phone, so we talked for like and hour about different roms, about drakaz and Galaxo and about how we got screwed over buying the Galaxy ofcourse. He seemed nice so i told him what roms i had on and that it wasnt a software error, since it stoped working without changing any settings and the guy wrote down the problems and send it to repairs, no questions asked. Was kindda risky though, he could have easily said i broke the phone using 3rd party software as i mentioned i had Galaxo on for a while, but as i said he was nice and that wasnt the case, lucky me
A week later i got it back ( was fast, it took 35 days for my Nokia repairs ) and there was ik4 installed ( im guesing coz its the last official release or was at that time ) and under repairs it said they changed some connector, nothing about updating my software, but im sure they did as i never had ik4 to begin with.

So, it wasn't software in my case and i realy doubt it was in yours.

EDIT: sry for my bad english, too lazy to go over it again