so im pretty much computer illiterate. ive gotten most of the emulators i have to work through trial and error. the one im working on right now is gngeo which ive gotten working except for the larger roms. when i try to run them in the emu. it says that a dumpgfx file must be created and asks if i want to create one. when i say yes it goes through and says it was successful, and i should select it again from the menu. when i do it starts to load and then bumps me back to the selector menu. any ideas what im doing wrong