mount /mnt/sd -o remount,noatime,nodiratime,sync
nice -20 ./beat2x
mount /mnt/sd -o remount,async
cd /usr/gp2x/
/usr/gp2x/gp2xmenu
I am not sure, but I figured that remount wouldn't work in a script like that since you're still using the filesystem. You might need to log in via serial or USB...