I have similar problem with CM11A. I use CM11A (without butteries) connected to USB and one TM13 Transceiver (code A1). Additionally I have MS13A wireless motion detector (disconnected now).
At the beginning CM11A and TM13 worked fine but after MS13A was added I stated getting error with wrong checksum. The problem still exists in my Beta 4. As I already said MS13A is disconnected. Here is a log:
10 03/06/08 13:30:40.013 Child device: #33(A1) Category:73 <0x41802950>
10 03/06/08 13:34:00.090 Receive string: MESSAGE 80 <0x41001950>
10 03/06/08 13:34:00.090 Received MESSAGE 80 0x62afb0 device: 32 <0x41001950>
10 03/06/08 13:34:00.090 Received Message type 1 ID 192 from 20 to 33 (device: 32) resp 0 <0x41001950>
10 03/06/08 13:34:00.090 Child device 33 has channel A1. <0x41001950>
10 03/06/08 13:34:00.139 Sending address with HouseCode=6, DeviceCode=6. <0x41802950>
10 03/06/08 13:34:00.139 Sending packet with HighByte=4, LowByte=66. <0x41802950>
10 03/06/08 13:34:00.139 Sending header with Checksum: 6a. <0x41802950>
10 03/06/08 13:34:00.583 Got response: 5a from CM11A. <0x41802950>
01 03/06/08 13:34:00.583 Bad checksum received (send:6a, recieved:5a). <0x41802950>
10 03/06/08 13:34:00.683 Sending address with HouseCode=6, DeviceCode=6. <0x41802950>
10 03/06/08 13:34:00.683 Sending packet with HighByte=4, LowByte=66. <0x41802950>
10 03/06/08 13:34:00.683 Sending header with Checksum: 6a. <0x41802950>
10 03/06/08 13:34:02.591 Got response: 98 from CM11A. <0x41802950>
01 03/06/08 13:34:02.591 Bad checksum received (send:6a, recieved:98). <0x41802950>
10 03/06/08 13:34:02.691 Sending address with HouseCode=6, DeviceCode=6. <0x41802950>
10 03/06/08 13:34:02.691 Sending packet with HighByte=4, LowByte=66. <0x41802950>
10 03/06/08 13:34:02.691 Sending header with Checksum: 6a. <0x41802950>
10 03/06/08 13:34:02.699 Got response: e6 from CM11A. <0x41802950>
01 03/06/08 13:34:02.699 Bad checksum received (send:6a, recieved:e6). <0x41802950>
10 03/06/08 13:34:02.799 Sending address with HouseCode=6, DeviceCode=6. <0x41802950>
10 03/06/08 13:34:02.799 Sending packet with HighByte=4, LowByte=66. <0x41802950>
10 03/06/08 13:34:02.799 Sending header with Checksum: 6a. <0x41802950>
Any idea what I do wrong?