Users logon to their netscaler site, then see list of applications, and if they click on any of the citrix desktops, it throws the below error and it doesnt start the desktop.

Solution:

downloaded receiver cleanup utility from the citrix downloads: http://support.citrix.com/article/CTX137494

The same can be downloaded from HERE

Removed existing citrix receiver using the above utility, installed reciever again manually. It resolved the issue.