Everything is working fine now, but I think it absolutely necessary to unplug your remote, I’ve entered the service mode with my remote (RM-MC10L, European version with display) plugged in and everything worked fine.
---add on
I looked back at the previous post and found out that you didn't mention the service mode but the switch between HeadPhone :arrow: LINE OUT.
I had found out myself that you can't change the setting when you've plugged the remote. Later after reading back some posts I found out that that what's you ment is stead of entering the service mode.
My version is 1.300, but Personal Disk Memory won't work. I've heard it before that this function didn't work properly with this tweak.