You never did mention exactly how much ram you have vice the amount of ram being used by the file? Also which operating system are you running? I know from experience that as bryce approaches 80% of your physical ram being used it starts swapping. This gets worse fast. Ive had a picture take 4 days of steady hardware swapping on the drives, installed more ram and test rendered the same pic at 17 hours. Therefore, if bryce is at 300 megs and you have only 256megs installed, your going to run into serious issues. I do understand the 45mins-hour opening a file though, happened to me on my last posted pic. The raw .br5 file was 720megs though, luckily zippable to 360megs to be burnt.