On the last SageCRM project I worked on, I ran across a little issue with the CRM interface which was causing me a bit of a headache. I was working with a couple of screens I had defined for a custom entity. These screens were similar, so I was doing a lot of comparing one screen to another. Every once and a while, I would notice that the screen contents would disappear from the screen I was reviewing, and I would end up having to rebuild the screen.
After rebuilding this screen for the Nth time, I figured out what was going on: If you change your mind and do not perform any changes to the screen, you MUST click either "save" or "cancel" to navigate off of the Screen Definition page. Leaving the Screen Definition by simply navigating off the page causes the defined contents to be stripped from the screen.
Of course, even after I figured that out, I still had to rebuild the view a few more times before leaving the view properly became second nature! Anyway, I hope this brief post saves you some headaches.
Thanks for reading!