Cave Story+ won't launch (Linux)

So I downloaded Cave Story+ thru Steam on my new Linux install the other day, and it ran perfectly. After I quit the game, I went to play it again later, but the game won't launch. Steam says its starting the game, then acts as if I just closed it (it says syncing and stuff). I have not changed anything on my computer since the initial successful launch. The logfile is also empty. If I attempt to launch the game from the executable instead of Steam, the game opens and runs fine, except that fullscreen spreads over both of my monitors, and is centered so that it is split across them. This did not happen when it launched through Steam; it went fullscreen on only my main monitor like it should.
I tried deleting all the game files and redownloading them through Steam again, but it didn't change anything.

Any ideas?