First, you may already do this, but please make sure you're saving incrementally(ie. first you save it as Konjakscap1.cap, next save Konjakscap2.cap, ... ...etc). Another option is dropbox, which keeps a history of file versions. So storing your cap in that folder would work as well.
It's rare, but there have been a few cases of cap corruption in the past. In my personal experience with file i/o, a crash during a save operation is a likely cause of data corruption in an otherwise reliable save system. If you're crashing frequently, again please make sure you're not saving over your only copy.
For the visual corruption of the IDE, make sure your graphics card drivers are up to date. I believe this is the first time I've heard of visual corruption like that.
Next thing I would do is save your game to a separate test cap so you can add random things, and save frequently, and do whatever to try to cause the crash. Before doing this, press Ctrl-Alt-Delete, and open task manager. Look for Construct.exe and watch the ram usage meter. Check to see how much it's going up when you do things like preview, or save, or whatever you normally do to cause the crash. I just tried this and there is a small amount of ram usage added on each preview. The first preview a large jump, and then much less afterward. 0 to 1MB per preview, and about 2 megs per save. It's small enough that I don't encounter this error at all, and save very frequently, and have been working most of every day all day in construct for a few months now. I have a crash now and then but it's usually related to either undo/redo operations, or trying to move events or groups around.
I'm not sure if the edittime shares any of the renderer code with the runtime, but after you get an idea of how much ram is leaking for each preview and save - try installing the new version to a different folder, like "c:/program files/construct r2/". If you save, make sure you don't overwrite your previous file, because the old version won't be able to load it anymore. Try to see if previewing and saving cause a smaller leak, if it does, then the problem's solved.
If not, I'm curious about the size of the cap on disk, the size of the RAM usage jump in task manager, and how much ram you have on your pc, and your gfx card vram. Also, does the error say anything else? or just "out of memory".
The cap I was using with task manager is one layout, and one event sheet with 762 events. If this is a problem directly with the editor, I probably won't be able to even attempt a fix, because I don't have the Prof-UIS library required to compile the edittime. Of the people still working on Construct Classic, Rojohound is the only one who does as far as I know. These things may help narrow down the problem in any case. And it could be that adding a little ram to your machine will at least bandaid the problem so you don't have to worry about it, even if the memory is leaking.
Lastly, do have any particularly huge image files? or an insane amount of images? I believe Arima said he had problems with large backgrounds messing up the IDE, and making it slow down. He said he fixed it by having the game load them from disk at runtime, at least during development. You could always disable those events and add the images to the cap just before release. lucid2012-03-10 13:13:46