Citrix Error - published_app failed to start. The Citrix Server is Unavailable to Process Your Request

Error: "[published_app_name] failed to start. The Citrix server is unable to process your request to start this published application at this time. Please try again later. If the problem persists, contact your administrator." when Connecting to a Published Application

The CMSTART registry entry maybe missing.
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Resolution:
start
run
regedit
navigate to:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\WindowsNT\CurrentVersion\Winlogon

AppSetup:Type = REG_SZ:

Ensure Data = CtxHide.exe UsrLogon.Cmd,cmstart.exe

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reference: http://support.citrix.com/article/CTX996187