CSS/CPPM is the protection applied to DVDs, imgburn should not have this (it does OK on some of the software protection methods though) as it was a fork of the increasingly good DVD burning side of DVD decrypter that lacked such abilities (DVD decrypter got shut down).
To this end you are going to want a DVD decrypting program, you could seek out DVD decrypter and it will work for the vast majority of DVDs but newer ones using methods like corrupt sector protection might pose an issue. To that end DVDfab (I believe the current extension of the free one is HD decrypter-
http://www.free-code...b_Decrypter.htm and
http://www.dvdfab.com/hd-decrypter.htm ) is probably the easiest to tell it to simply work.