A user called in, saying that she was having problems with her email client on Citrix. I quickly established that she was using a Mac, and that she was able to open and read emails, as well as start a reply, but that no keyboard input seemed to show up when she was writing an email. I next asked her to try to search in Outlook, with the same result. The final thing we tried before ascertaining what the problem was, was checking if the problem only affected Outlook. As it turned out, it didn’t, but propagated through all applications in Citrix.
A quick Google search led me to the conclusion that the problem was most likely caused by a problem in Citrix Receiver versions prior to version 11.9. I logged on to Citrix Director, and lo and behold, she was using version 11.8.2:
Having established this, the solution was simple enough; download and install the most recent version of Citrix Receiver. Problem: solved.