I'm sorry - I was in a hurry.
I set the MaxConcurrentRequestsPerCPU to 5000, restarted the IIS, then I set it to 10000 restarted the IIS - same error number. Then I noticed that the default web site was running under ASP .net 1.1 - and I switched it to asp .net 2.0 but I get the same error as before - Error 1818 CallCancelled.