So out of the blue after upgrading to a newer JRE our NetScaler Admin GUI stopped functioning, resulting in a nice JRE error:

Java Applet could not be loaded and then some possible reasons that don’t add up. This is another frustrating issue in the NetScaler Java GUI which isn’t working in general. I hope Citrix speeds up there HTTP console development. Anyway you can fix this (or at least work around it) disabling the Java Deployment Cache.

Navigate to the control panel > programs > java > click settings in the temp internet location and uncheck keep temporary files. Alternatively you can do so by modifying the following regkey:

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\AppDataLow\Software\JavaSoft\DeploymentProperties]
"deployment.cache.enabled"="false"