First, make sure you have adb installed & that it can pick up your device. Next, adb shell into your device & type the following commands:
su
mount -o remount,rw -t yaffs2 /dev/block/mtdblock3 /system
cd /system/etc/security
mv otacerts.zip otacerts.zip.bak
mount -o ro,remount -t yaffs2 /dev/block/mtdblock3 /system
sync
reboot
mount -o remount,rw -t yaffs2 /dev/block/mtdblock3 /system
cd /system/etc/security
mv otacerts.zip otacerts.zip.bak
mount -o ro,remount -t yaffs2 /dev/block/mtdblock3 /system
sync
reboot