With the update to Mac OS X Yosemite, my Citrix Receiver–which I need for accessing customer systems–suddenly stopped working. I do not know if or why the problem is caused by the update, but it stopped working on both–my iMac and my Macbook Air–at the same point of, meaning with the Mac OSX update. For those Mac and Citrix users having the same problem, I want to provide a quick solution.
The reason for Citrix Receiver not working properly are invalid file permissions in the app specific folder in $HOME/Library. This can easily be fixed, changing the permissions with this simple Terminal command (quick and dirty setting the specific directory to writeable for everyone):
chmod 777 $HOME/Library/Application\ Support/Citrix\ Receiver/Modules