WCF works only with the Web.config is checked for edition

Question

I've a problem. I've created a WCF in .Net 4.0. This is the contract used:

    [OperationContract(IsOneWay = true)]
    void Proccess(byte [] importRequest, int idTask);

The service works fine only when the web.config for the WCF is checked for edition ("Check out" mode). When I do a "check in" the web.config file switch and the service does not work.

BUT, if I "check out" the web.config (without any change), the service works again.

When the web.config isn't checked for edition, the application calls to "Proccess" and continue without throw any error but the service is never executed.

Any idea?