Ajax GetCallbackResult() function problem

Hello all !

I have problem with Ajax callback functions, I have small chat onASP WebForms, it works fine but some time (and I dont now when and why it is not predictable), some packages not sends to the client fromGetCallbackResult()  function,

I log all behaviour of this function and it sends data to client but client (Browser) not receives that one in some cases;

Plaese help me, what may be the reason.

Thank you.

Note:

On the same page also I have Updatepanel, I note that callback data losts when update panel updates itself by timer and callback function receives data simultaniously