Few things:
– Just like Jim, I experience all the same problems that you do IF I have AE opened with a dynamically linked project. When I quit AE all the problems go away.
– Check your GPU acceleration, and whether it is set to on or off, try the other way. GPU acceleration is much faster but whenever there is a strange issue it is often the source.
– Don’t edit too much H.264. While Premiere can handle it, it’s an inter-frame codec, meaning most frames are referencing another frame 4 or 5 away. This adds to the processing needs. While it’s probably too late for this project, future projects with a decent amount of DSLR footage should have it converted to ProRes 422 before going into Premiere.
– In my experience, CC 2014 is pretty buggy, and for future projects you might consider going back to CC until some of these issues are ironed out.