Disable Session Reliability in XenApp 6
One of the requirements of published apps in citrix is to limit the user to a single instance of a published application. In xenapp 6, the checkbox in the published application properties that states limit the user to one session does not seem to do the trick by itself and often brings about errors. Users receive errors like "the server has reached the maximum number of connections" and others of similar effect.
So what everyone does is uncheck the box and find what is different about xenapp 6 or even worse think there is a larger problem with their xenapp 6 installation. The solution is simple enough.
Limiting session for a user to one per app can be accomplished using a policy. Create a new computer policy for the farm and disable session reliability. Once session reliability is turned off, check the box in application properties to permit only one instance of the published app .