搞定了.
原来是因为两个objectUri的值一样.将之区分开,然后在客户端也做下改动即可SERVER:
 <service>
            <wellknown 
            mode="Singleton" 
            type="CDBAccess.AllAboutDataBase.CDBAccess, AllAboutDataBase" 
            objectUri="AllAboutDataBase"
/>
         </service>
         <service>
         <wellknown 
               mode="Singleton" 
               type="FileTrans.CFileTrans, FileTrans" 
               objectUri="FileTrans"
            />
         </service>CLIENT:
   <client>
            <wellknown 
               type="CDBAccess.AllAboutDataBase.CDBAccess, AllAboutDataBase"
               url="http://192.168.0.168:9990/AllAboutDataBase"
            />
        </client>
         <client>
             <wellknown 
               type="FileTrans.CFileTrans, FileTrans"
               url="http://192.168.0.168:9990/FileTrans"
            />
        </client>