I have and ISA server protecting two CITRIX NFUSE servers and another WWW server. The WWW server is performing OK. The CITRIX IIS service stops for no apparent reason. If you http://localhost a web server security error or Digest authentication error occurs. Restarting the IIS server from the IIS manager or iisreset /restart resolves the problem for a couple of hours. The IIS logs and ISA URLSCAN logs do not indicate any problems nor does the Event log on the CITRIX servers. Restarting the CITRIX XML service does not resolve the problem. Thus I believe it is an IIS problem. I wonder if a special configuration is required for URLSCAN on ISA for CITRIX NFUSE and OWA to resolve this problem. The ISA server is W2K3, ISA standard in Integrated mode with authentication enabled for the ISA logs. Thanks in advance Darryl Janetzki