Recently I upgraded from PE10 to PE15 and from the outset, I was really impressed by the change in processing speed. Hour long videos would render in about 50 minutes versus the PE10 time of about 4 hours. Same Dell Laptop PC, just upgraded software. After about 10 different renders at that 50 minute speed, the last two renders have reverted to the 4 hour time frame that I was experiencing with PE10. I have kept memory consumption at very low levels so why is the processing speed all of a sudden slowing down?