Possible fix to help Marbles on Stream run smoother
Something Pixel noticed was that moving the installation location for your Steam Games out of the "Program Files" folder. Steam defaults installs to this folder but if you move it to it's own folder it might help things run smoother. This was noticed when Pixel was playing Marbles and other games.
Mainly uninstall all of Steam and your games (be sure to save your game and save files in case!). Reinstall Steam and direct your games folder as stated. This just might help in Marbles and your other games as well!
Bonus: This might also help your other games run better as well!
Follow the steps in the link to change the location of your Steam game installations.
Moving a Steam Installation and Games