How do I fix it? Does Camtasia Studio 8.6 hate me?
It's all about resources. Even when rendering, your graphics card is still in the mix. Best standard of equipment. Quad Core 3+ ghtz, 8 gig ram, dedicated video card (as long as it's not a GPU in your CPU) with that said, take pieces of your production and pre-render them. Then import those to a new project and assemble. Turn 10-15 tracks of all sorts of video layers, call outs, images, graphics, etc into 5-6 HD videos and bring them together. Making them library assets from your timeline doesn't render them, so when you add them to a timeline in a new project it still eats up resources. Having 4-5 video pre-renders is a pain in the ass if you want to go back and change a section, but it will get the job done. It also helps to give you an idea as to how much your system can handle