"I accidentally downgraded my CS from software version 1.1.3 (0) to software version 1.0.5 (3). Now it won't boot anymore. How can I fix this?"

And the reply:
"How to fix it:

1. Prepare an USB memory stick without files in the root directory (sub-directories may exist).
2. Copy the following files into the root directory on the stick: stick.sh and reparatur.sh
3. Power up Central Station 2 with inserted USB Stick
4. Wait till the program starts - this may take up to 5 minutes.
5. Go to Menu Setup and select [Shutdown] ([Herunterfahren])
6. Remove the USB stick after shutdown completed.
7. Delete reparatur.sh and stick.sh from the USB stick.
8. Both stick and Central Station contain a backup of the configuration data.

Files stick.sh and reparatur.sh are attached to this post."
(see M* FAQ for attachments)