Underneath the linux port(I don't know if this is true for other ports), I play Gish on my laptop. Sometimes I hook it up to the TV, so my max resolution is lower than the internal LCD is. When I play with the LCD, I have my resolution set to 1024x768, and for the TV, 800x600, but if I enter gish while gish was set to 1024x768, and it's now on the TV out at a max of 800x600, gish crashes.
Ie, if the resolution in the config is higher than the current max for the windowing environment, gish crashes, at least for if it was set before entering Gish.
It's also possible it's an SDL bug, but who knows.
I think it is an SDL bug. It happens for me as well, since I am running Gish on my laptop with two screens attached. The main screen is 1280x768, the secondary is 1280x1024. It happens for other SDL games as well.