Cannot connect to the Citrix XenAPP server

I wonder if some one can help me on this issue?

Server 2008 R2, Xenapp 6

For our streamed application since last week few users are having this error:

Unable to Launch your application. Contact your help desk with the following information: Cannot connect to the Citrix XenAPP server, the server (Unknown) is not trusted for ICA connections. Connections to all Allregions are not allowed by lockdown settings. Please contact your administrator.

wiered thing is its not effecting all the users, I tried changing registery:
HKEY_CURRENT_USER\Software\Citrix\ICA Client as per below:

Tried GP as per below:

But still no joy. any idea what this problem is and how can we fix it?

Your help as usual would be highly appreciated.

Thanks Sohail

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nhsconfedConnect With a Mentor Author Commented:
From one of the working user, HKCU, i exported the citrix reg keys and imported to affected user, it did the trick.

Thanks all for the help.
Can you temporarily disable GPOs to the XenApp server and try it clean that way. If it works then add back each GPO to see when the problem breaks. Once it breaks again look at the specific configs within that GPO that is causing the problem and we should be able to narrow it down
nhsconfedAuthor Commented:
This was the first thing I did, Disabled the GPO completely, GPupdate /force, rebooted the terminal server (infact couple of reboots) No Joy,

Googled the issue and found above links, implement above but no Joy.

I personally don't think its GPO, GPO is applied globally to all the users, yet few users are infected only.

Any more ideas would be highly appreciated.

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is there a common profile or region, or attribute about the users that are able to connect with no problem. Could they be power users, or listed in a different AD group.

What about network filters and restriction policies? Just trying to get a better grasp of the problem.
Lee OsborneCommented:
Have you tried unchecking the trust xml connections option for the server(s)?

Sorry, I wrote the following resolution out for XenApp 5 and then realised you need XenApp 6! I can't remember off hand where this setting is in the Policies for XenApp 6, but give it a go. The XML Service setting should still be application in v6.

(XenApp 5 Version) Citrix AMC > (Right Click) <servername> > Properties > XML Service

Uncheck the option: Trust requests sent to the XML Service.

nhsconfedAuthor Commented:
Thanks Lee,

In XenAPP 6, this option is in Policies, there are two options there, Enable trust XML or Disable. It was enabled so I disabled it unfortunately it has made no difference,

We have logged a call with experts now and they are coming to see this problem, as there is no solution I can find anywhere.

nhsconfedAuthor Commented:
Thsi was fix research on different artciles by citrix.
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