Download script manager from the market and run this script
clear
echo "mounting system as read-write"
mount -o rw,remount -t rootfs /
echo "unmounting /cache"
umount /cache
echo "removing directory -- /cache"
rmdir /cache
echo "creating directory -- /mnt/sdcard/market_cache"
mkdir /mnt/sdcard/market_cache
echo "creating symlink -- /mnt/sdcard/market_cache -> /cache"
ln -s /mnt/sdcard/market_cache /cache
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