@ OP, you should try downgrading the firmware, 4.0.0 isnt that much use on a f100. Dig through some old threads here to read up on howto.
I use fw 2.1.1 with Notaz's excellent SDHC firmware patch:
http://notaz.gp2x.de/other.php#GP2X
http://www.gp32x.de/board/index.php?showtopic=35840