The more stuff you add to the game, obviously the more memorry the game whats to grab, and the more memory is there for the game to lose.
Something I have found to help the game is if you've changed the exe that you use to run the game into something other then strandedII then that might cause some problems when the game TRY's to debug lost memory...
Don't be running tons of programs while you play stranded and that might help as well.
At least, thats my unprofessional idea... I don't have a professional idea.