For CD-RW's I do 4X and for DVD's I do 2X. All depends on your Xbox DVD drive. I've done CD-R's at 16X and they've loaded in the Samsung DVD drive no problem. RustyDog
I allways burn @ the highest speed.DVD-r 4x or 2x with 2x Media.48x cd-r and 10x cd-rw. Been able to get all burn games,dvd's to work with all 3 type of dvd drives out there. All you need to find out is a reliable dvd Media that works with all 3.
As i say i am new to this but i guess it must be down to your own drive? A friend of mine is having trouble with his backups , We have both brought the same media and have both been burning at 4 speed but not with the same results. He seems to be getting alot of stop start and freezing up. I have a Samsung drive and i am having no problems at all, and i have been told they are alot more forgiving.