For those of you who have recently upgraded to OSX Snow Leopard, I hope you notice that Safari is now 64BIT natively. This is great except for the fact Citrix does not play so well with 64BIT browsing on the Mac. If you notice nothing happens when you try to launch applications through a Web Interface site, or through Access Gateway (Netscaler or not) it is because you are running Safari in 64BIT - which is the default setting.
To resolve this "feature" you will need to put Safari in 32bit mode or download and use Firefox. To put Safari in 32bit mode, just right click the icon and "Get Info". You will see a place for a tick mark for "32bit mode".
This has become an issue here where I work, and I have voiced my concerns to both Citrix and on the Customer Advisory forums. All we can do now is use this work around until they release a fix.