Citrix Xenapp 6.0 gives an error when users logon to the citrix web interface "An error occured when making the requested connection"

This error can occur because of a number of reasons concerning the Xenapp 6.0 server. Besides the obvious reason - the server does not have internet connectivity or is shut down, the tricky cause can be the load value for the server. This can be checked using the following command on the culprit Xenapp 6.0 server

QFARM /LOAD

This command will give you the list of the servers in the farm and their load value. If the load value of the server is 20000, it will refuse any further connections and give the above error. One more symptom is that you might not see the server in the list at all. This can be corrected by doing the following

1. Open Command prompt as administrator

2. Run the command "net stop imaservice" to stop the imaservice

3. Run the command "net start imaservice" to start the imaservice

NOTE: this can also be done through services.msc console but i have experienced that the imaservice tends to hang when restarted through services console. 

Once the service is restarted. The server will start accepting connections again.