Some users have reported that the newest version of MacUpdate Desktop (6.1.1) is not running correctly on OS X 10.9 Mavericks.

To make sure that you can continue using MacUpdate Desktop and all of its features, please download version 6.1 here: MacUpdate Desktop

After downloading and installing version 6.1, send us a support ticket here: so that we can work with you on getting 6.1.1 working.