I'm not sure but i think i know the Prob!
I use an external Keyboard with German Layout, the Softkeyboard works with some registry changes.
The external Keyboard use maybe the Registrykey HKEY_LOCAL_MACHINE\HARDWARE\DEVICEMAP\KEYBD
The important Values are:
Type 4 is for english, and i don't know the german value, i think it is dangerous to change it to any value, without know how.
Maybe also the prob is the Key:
If it is the problem you must generate a german driver with the SDK!
As i said before, i'am not sure but this are my results and i'am also looking for a solution!
I hope that was a little help!