TIP: NetScaler 10.5 uses HTML5 instead or JRE for most configuration features! Hooraaayyy! – link
On January 14 Oracle released Java Runtime Environment (JRE) 7 update 51. Just like previous updates the raised the security level which could potentially break existing applications. We saw the same when they released 7u45, back then I found a more constructive (but complex) solution to solve a problem where the GUI hanged at “Downloading Applet..”
Citrix updated their NetScaler software to meet the requirements of Oracle on December 3rd (download, release notes) – I hope that back then you reverted to a more secure JRE. Unfortunately JRE 7u51 gave me again problems, this time the Java Applet could not be loaded.