I've got the same problem with Fhem. Does anybody know where to change that in the fhem Module?

Had the same Problem!
I'm totaly new to MYSENSORs and my gateway runs on an Arduino pro mini 8MHz attatched to a Pi.
Funny thing was that the controller is able to send data at 115.2kbaud but can't read at that speed when clocked with 8MHz ( as explained here : http://forum.mysensors.org/topic/1483/trouble-with-115200-baud-on-3-3v-8mhz-arduino-like-serial-gateway-solution-change-baudrate).
Solution: Set your baudrate to 57600 end reupload the sketch.
Took me quite a while bevor I figured that one out.

Hope that helps anyone how encounters the same Problem.