Cannot connect to the Citrix MetaFrame server.Can't assign requested address.
网上虽然有很多办法，但是都不管用，即便是官方网站上面所说，一样不能解决，后来仔细的回忆了出现问题的过程，想想应该是给服务器升级补丁后，重启服务器后导致Citrix的相关服务不能正常运行。
解决方法：再安装Citrix MetaFrame FR3的SP4升级包，重启服务器后，客户登录，结果正常。
下面给出官方的解决说明：
Error: Cannot Connect to the Citrix Server. Can't Assign Requested AddressDocument ID: CTX965513 / Created On: 2001-10-10 / Updated On: 2003-10-9
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Issue 1:
Connections to an application set cannot be made. But, custom ICA connections to server desktops and published applications are successful.
Error: Cannot Connect to the Citrix Server. Can't Assign Requested Address
Cause:
This error message occurs if a server(s) is moved from one zone to another zone and is not rebooted.
Resolution:
Reboot the Citrix server that was moved from one zone to another.
Issue2:
No connection to an application set or a custom ICA connection can be made, but RDP is fine.
Cause:
Unknown
Resolution:
Recreate the local host cache (LHC)
To recreate the LHC with XP FR1 or later:
1. Stop the IMA service
2. In a command prompt type: dsmaint recreatelhc
3. Start the IMA service
For more information on the LHC please see document Function of the Local Host Cache on MetaFrame XP