Linq to sql stop working

hey, I have strange problem, i've built a prject using the Linq, and most of it works fine, However sometimes all the Linq's Repository commands stop working, and i'm geeting errors, the issue solve when i overwrtie the existig dll files of the Linq project? maybe one bad command hurt the rest to the开发者_Go百科 Datacontext? the Question is how can i deal with it?

Thanks,

etc, im getting some kind of errors like the following: A transport-level error has occurred when sending the request to the server. (provider: TCP Provider, error: 0 - An existing connection was forcibly closed by the remote host.)