I have not noticed any problems with serial communication since upgrading to beta 11.

There is a known problem with the config.ini file, documented here which might have a bearing. Check that.

At absolute worst, you should be able to do the following:

- Remove power from the car player.
- Run the 1.03 upgrade file.
- When the upgrade software prompts you to apply power to the player, do so.

That procedure completely bypasses all code on the player's hard disk and kernel, and directly flashes a new software build. So if beta 11 is giving you trouble, try that and see if everything goes back to normal.