Symptoms
Users can log on to Web Interface 4.0 through Secure Gateway 3.0, but when attempting to launch a connection the following error message is returned in the Message Center:
“Error: An error has occurred while connecting to the requested resource.”

When you try to right-click and save the launch.ica file to the desktop, the following error message appears:
“Internet Explorer cannot download …”

Web Interface may show an Event ID 0.
"Event Type: Error
Event Source: Web Interface at c:\inetpub\wwwroot\Citrix\MetaFrame
Event Category: None
Event ID: 0
Date: 6/28/2007
Time: 2:10:48 PM
User: N/A
Computer: YourServerName
Description: The MetaFrame servers reported that they are too busy to launch the selected item. This was reported from the XML Service at address "YourFQDN/IPAddress". [Log ID: aa185a20]
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp."
- Or -
"Event Type: Error
Event Source: Web Interface at c:\inetpub\wwwroot\Citrix\MetaFrame
Event Category: None
Event ID: 0
Date: 6/4/2008
Time: 1:40:49 PM
User: N/A
Computer: YourServerName
Description:
The MetaFrame servers reported that the alternate address cannot be found. This was reported from the XML Service at address "http://YourFQDN/IPAddress:XMLPort". [Log ID: 520de53a]
For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp."
Cause 1
There is a syntax error in the Web Interface configuration under “Edit Secure Gateway Settings” for the STA address.
Cause 2
The Citrix XML broker service may have an unstable Citrix XML Service at the address specified in the Event Viewer Description field.
Cause 3
The Presentation Server reaches full load and rejects any new connections.
Cause 4
One or more of the Presentation Servers that publish applications do not have the alternate address defined.
Resolution 1
Adding the STA port to the Secure Ticket Authority URL resolves the problem:
http://servername:8080/scripts/CtxSTA.dll
Resolution 2
Restart the Citrix XML Service on the address specified in the Event Viewer Description field.
Resolution 3
Issue the qfarm / load command to check the load status of the servers running Presentation Server and change the load evaluator if needed.
Resolution 4
1. Open a command prompt on Presentation Server and run the altaddr command.
2. Make sure the alternate address is shown. If it is not shown, run the altaddr /set <AlternateIPAddress> command.
More Information
CTX584485 – Configuring NFuse/Web Interface for Use with Network Address Translation (NAT)
CTX039746 – IMA and ICA Browsing With Firewall Address Translation (NAT)
CTX105313 – Error: An Alternate Address has not been set on the MetaFrame XP Presentation Server