Message text is sent but stays in the box

I have a user who types a message in the client and it is sent, but the message stays in the composition box so she ends up sending repeated messages. Any idea what may be causing this odd behavior?

This is a know issue with spark 2.5.8 on windows. The only cure I have found for this issue is to:

  1. Uninstall spark 2.5.8
  2. Delete the residual Spark folders (Program Files and in the User Profile Folder for the user with the issue)
  3. Install the latest 2.6 beta build of spark without the included JRE (http://www.igniterealtime.org/community/docs/DOC-1822)