I've got the same problem.
I can't make any progress on my game because every so often Construct randomly decides to tell me "OUT OF MEMORY" when I save, and I have to revert to the most recent backup copy of my game. When it does this, it renders my current .cap useless and corrupt.
Originally I was under the impression that this was because I was cramming too many super-high-res background layers in, but alas, it seems to be a random bug.
Please help me, I unfortunately have not been making backup copies every five seconds and now must leave Construct and my computer running until I find a solution.