connection failed to the server

[Battosaiii]

I get this message of error when i get connected to the server i made on the computer:

java.lang.NoClassDefFoundError: ClientDoctor/BufferedInputStream

I have made a Client and a server. The problem is : each time I have I tried to connect to the server with a emulator a pop up appears saying :
"Midlet wants to receive information is this ok ?" with a noise .
Then the windows shuts down if i says ok. If i says no the applications is still there but it doesn't process the application.

i did try for Prototype_3_0_Nokia_7710_MIDP_Emulator and
Prototype_4_0_Nokia_7710_MIDP_Emulator. I did try many of them but nothing happens. But yesterday the client correctly connected to the server . What is the problem ?
Why ?

[Battosaiii]

I dont understand why it does not work ! Please help i am stuck on this