Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Though I don't know what upgrade exactly your iMac received, I would presume you mean an upgrade to the MAC OS X version.
If so, I recommend that you back up all data to a sparate device, then uninstall QX, and restart your computer, then reinstall QX.
(Please consider that it is Sunday, and fewer Experts are working today perhaps.)
What version of QX is it, and what upgrade was it?