As stated here (http://vsido.org/index.php?topic=992.msg11479#msg11479) there is no longer a need for VirtualBox Guest Additions on the VSIDO ISO. This has already been removed from the current ISO's
To uninstall the Guest Additions from a VSIDO installation do this:
cd /opt/<VirtualBoxAdditions-x.x.xx>/
sudo ./uninstall.sh