I've been using Windows Movie Maker 2012 over the years, first on Windows 7 and now 8 for the last couple of years, and I've struggled for a while to track down a nagging bug. I wanted to post my experience here in the hopes that it can help others, because I haven't seen anyone describe the solution I discovered.

The symptoms were that I would be clipping out unwanted sections from footage, when things would just stop working - the video won't play, nothing can be trimmed, the arrow keys don't navigate the clips anymore, there's just a black screen showing, and if you try to save the project, it doesn't respond. Although, you are still able to close the program. Sort of. There will be a zombie process left behind.

After killing that off and relaunching, I'm immediately asked to recover my last project. When you say yes though, it's back to the same issues as before.

I had some initial success tweaking on the project file based on changes I could see from last-known good saved projects as I edited, but this only worked to a point.

What it came down to had nothing to do with drivers, file formats or system resources/hardware. Rather, it was Media Maker's ability to handle extremely short clips. Although it does have the ability to handle them, you have to play close attention to the zoom level slider at the bottom of the window.

If you zoom all the way in, you have the highest chance of success at editing very short (<1 second) clips. Apparently there is an issue with how the program tries to scale the clip's entry in the timeline whose length falls below the minimum size imposed on a timeline entry.

If I encounter this problem now, I will try to undo the slicing I did and save safely, or if I am forced to, kill the hanging process and reload anew. Once I have a fresh copy running, I load up a known good project file and slide the zoom all the way to the right, and then quit. You don't have to save your changes. In fact, you'll notice that the change made to the zoom slider stays with Movie Maker the next time you run it. The zoom MUST be pre-set to maximum before you reload the video giving you issues - it cannot be zoomed in after loading, it's already broken at that point.

Best,

-Eric