I’ve only noticed this problem with a Windows Vista machine, but from researching the issue I understand it can happen on several OS depending on what is running in the background that is stealing focus from the Application you’re currently working with.
One guy had a problem of losing focus completely, that is, he could be doing something like typing and all of a sudden his keystrokes weren’t registering and he’d have to click on the application again to give it back focus. In his case, he had a program running called Changer XP that was messing with him. My issue is similar but manifests in two ways:
1. I had iTunes, a folder of pictures and Adobe Photoshop CS3 open and was working on editing a couple pictures. As the system was just sitting there, I saw it flip from PS to the folder and then back again. Trippy huh?
2. The other issue is a huge annoyance. Whenever I’m watching full-screen video in Netflix the screen will suddenly and unexpectedly exit the full-screen mode causing me to have to click it again.
I don’t know the cause yet, but I have reason to suspect the file system is running some process that is stealing focus temporarily causing these effects. The primary suspect is my ESET antivirus. It would make sense that real-time virus protection could be stealing focus. It is interesting to note that I have the same AV running on an XP box but that one has no problems. Might be an issue with ESET–VISTA. I will have to try disabling the antivirus and play a Netflix video to see if that’s the cause.
Here is something to try in the Registry too: http://askville.amazon.com/Vista-application-focus-current-window/AnswerViewer.do?requestId=8758657
Update 1/2/2010 - After watching 3 or 4 episodes of Man vs Wild I can now tell you what the problem was… It was due to having another profile logged in while I was on mine. So what you need to do to get Netflix to stay fullscreen is Switch User and Log Off that profile. Should solve your problem and make Netflix stay fullscreen mode.