I ran into a similar issue recently, and it turned out I had connected to my ISY via https instead of http. That caused intermittent errors in the console, and made it load pages extremely slowly.
So make sure you're using a http:// URL to access your Console! (Toosl > About, and it'll show "My URL" there).
Also make sure your Firmware and UI versions match -- I had also been using an old launcher so the UI was version 4.x and the firmware was 5.3.4 and that caused some issues too.