I havent seen g4.5 yet, but i would maybe check the vsync option and see if that is on and if it is i would try taking that off and try the fields again. If that doesnt work i would put it back on if it is at first and go through 1 video setting at a time and dropping it down 1 click to see if it quits having issues on you. Also set every video setting to a medium setting at first and try to run the maps. IF they work but the quality doesnt look as good you can do individual settings and up the settings till you can still run it yet it looks better. I have fsone and have a very very good computer that i personally built and when i tryed upping the video settings i would have the same issues you are describing.