I receive the following error text at logon and it doesn't stop even if I choose "Ignore":
Error: KBMReadyCheck/ReadyCheck.lua:1576: attempt to index field 'Header' (a nil value)
In KBMReadyCheck / KBM Ready Check Synchronized Start, event Event.Addon.Load.End
stack traceback:
[C]: in function '__index'
KBMReadyCheck/ReadyCheck.lua:1576: in function 'ApplySettings'
KBMReadyCheck/ReadyCheck.lua:2458: in function 'Update'
KBMReadyCheck/ReadyCheck.lua:2473: in function 'UpdateSMode'
KBMReadyCheck/ReadyCheck.lua:2689: in function <KBMReadyCheck/ReadyCheck.lua:2672>

Sorry about that, it seem to be related to the german translation.
I have fixed the problem for now, but i will have to find a more permanent fix later.