最近给客户上系统的时候，也是使用Citrix做为支持平台，可是发生了几次类似的错误：
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