I'm sorry you were not able to fix the resolution problem :(
I have no other suggestion to help you, maybe someone else will be more helpful :)
I don't think that BSplayer requires high performance Graphic Cards, it's the less expensive player in CPU and Memory usage on the market
Maybe you can try old (0.86.501) version of BSplayer, you can find it
Here and
Here. It consumes even less resources, but as I already said, I don't think it's a low memory grphic card problem.
Stay tuned, and good luck for your problem!! :)