FINALLY found that annoying glitch where everything jumps forward or backward up to a second. Just had to completely rewrite the time keeping system in the graphics engine, (Geez was getting negative time
This problem was kind of rare, but it was in there. It's only recently that I tracked it down to a timing glitch. The sim runs smooth as silk now. I think I'll be spending all week working on improvements to the user interface. All based on user feedback.