we sometimes receive Http 400 bad request resultcodes when posting a large file (10mb) to a WCF service hosted in IIS 6. We can reproduce this using SOAP UI and it seems that it is unpredictable when this happens. In our WCF log the call is not received, so we believe that the request does not reach the ASP.NET nor WCF runtime. This happens on multiple websites on the same machine each having their own application pool. All IIS settings are default, only in ASP.NET and WCF we allow bigger readerQuota's etc....
The win32status that is logged in the IIS log is 1450 which we think means "error no system resources".
So now the question: a) how can we solve this b) (when a is not applicable :) ) which performance counters or logs are usefull to learn more about this problem?