it's probably because you're using 1280x1024. I'm pretty sure it's treating it like a 2048x2048 texture, which is rather massive. Also, transitions cause all kinds of bugs atm, so I wouldn't recommend using them. I haven't fully tested all of them out, so it may be only certain transitions which are buggy. Fade to black might just work, but heed my warning and realize that they can cause graphical glitches and bugs. Use at your own risk.