This is a typical problem with newly installed Citrix Web servers.
You may see a very long response time for the users to get to the welcome screen.
This is often when you have restarted IIS or the web site has not been used lately.
To fix this start a command prompt as administrator.
Insert the text <generatePublisherEvidence enabled=”false”/> as show here:
Do the same for the 64 bit version in c:WindowsMicrosoft.NETFramework64v2.0.50727Aspnet.config
More information can be found here http://support.citrix.com/article/CTX117273
Another tip that seem to have a good performance impact on Application Enumeration is to disable NetBIOS over TCP/IP: