The server will drop the connection, because the client driver has sent multiple requests while the session is in single-user mode. This error occurs when a client sends a request to reset the connection while there are batches still running in the session, or when the client sends a request while the session is resetting a connection. Please contact the client driver vendor.
Synchronisation process some time work and mostly fails. I have 5 client of sql CE that need to sync and i am using WCF IIS and sql 2008 for this process.