This error is typically experienced by users running Mac OS X 10.7 & 10.6 with either the Citrix 11.4.3 Receiver or the Citrix 11.5 Receiver and is addressed by rolling back to a previous supported version of the Citrix plug-in.

Follow these steps to roll back to a previous version of Citrix:
  1. Uninstall the previous version of Citrix using the uninstall program provided by Citrix.
  2. Browse to the Citrix Download page for Citrix Online Plug-in 11.2.
  3. Click Download next to Citrix Online web plug-in – Version 11.2 (18.2 MB)
  4. Select "Download your file manually" to download the file without using the download manager
  5. Once the file is downloaded, double click the CitrixOnlinePlug-in_web11_2.dmg. This runs the Disk Utility program, which mounts the file as a disk image accessible from your Mac Desktop.
  6. Double click the Citrix Online Plug-In disk image from your desktop.
  7. Double click Install Citrix Online Plug-in.pkg and follow the prompts.
  8. "The installation was successful", click Close.