It seems like memory corruption, the most annoying kind of bug. Might take some time to fix, I haven't been able to reproduce it on my computer.
I get the same bug as DeaDTerra. Let me know if I can help test, or if you need a pastebin dump to figure it out. I am trying all sorts of settings but still get the same issue, running on Win8, 64bit. I get the same issue on three other PCs. The most it runs for is a minute or so.