Yeah, my advice still stands: Either use "tripwires" to turn on torches in your immediate area, split up the map into smaller chunks, or simply reduce the number of pictures on the screen at once.
If it doesn't seem like RAM is the problem here, it might just be too much competition for CPU cycles.. turn off other stuff in the background that you take for granted, or try setting the RPG_RT.exe to high priority. GO RPG MAKER GO