This document contains information on issues that are reported when using Citrix Access Gateway VPN Client with Mac OS X 10.8 (Mountain Lion). An attempt to connect to a VPN tunnel fails and possibly crashes the machine.
The Access Gateway VPN Client (all versions) is currently not supported with Mac OS X 10.8 Mountain Lion.
Citrix recommends uninstalling the plug-in. At this time, there is no workaround for the Access Gateway VPN Clients when using Mac OS X 10.8 Mountain Lion.
Citrix is currently investigating this issue.
Read the original post here at the Citrix Knowledgebase.