Protocol error: 400

I got error when I connect  Motorola MC65  device with operating system Windows Mobile 6.5.The Device register to the server successfully  but  it can't synchronize from the Server .

the server log show :

ERROR Mobilink Thread-249 [com.sybase.ml.sup.Logger] [-10117]Stream Error: Unable to continue unknown HTTP session

ERROR Mobilink Thread-240 [com.sybase.ml.sup.Logger] [-10001]Protocol error: 400

The device catch error Log :

iAnywhere.Data.UltraLite.ULException: MobiLink communication error -- code: 86, parameter: 404, system code: 0

Thanks in advance