How to get the Citrix Receiver for Windows 4.1 to work with XenApp 4 for UNIX

I still support an old XenApp 4 for UNIX Farm. Any Citrix Client over version 12.1.44.1 does not work correctly. The App loads but does not draw the screen correctly, leaving the app seemed either greyed out or just blue.

To workaround this, add the following to each client. I use a GPO to deploy the settings.

On a 64 Bit Windows OS:
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Citrix\ICA Client\Engine\Lockdown Profiles\All Regions\Lockdown\Virtual Channels\Seamless Windows, DeferredUpdateMode, REG_SZ, false

On a 32 bit Windows OS:
HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\ICA Client\Engine\Lockdown Profiles\All Regions\Lockdown\Virtual Channels\Seamless Windows, DeferredUpdateMode, REG_SZ, false

As a side note, anyone still using a Presentation Server 4 Farm (yikes), this will also work for you, too.