See if there's some kind of .ini or .cfg file in the SNES9XW directory, and if so, delete it (or more safely, move it to somewhere else). That should reset the config options for the program and it should load the defaults, hopefully. If it worked before but now it doesn't, you might've messed up a graphics or sound (who knows) option in the program. You could try reinstalling the program somewhere else too and copying your ROMs and savegame / savestates over so you don't lose them all.