Something strange happens on my peg.

Some DVDs works without problems, but some others make only read/write errors. They work fine on my stand-alone DVD player and they are clean.

Is it possible to be the filesystem? Or Does I have to bye a new DVD-rom?

I have same effect with encrypted DVDs (when I try to open the .VOB file with mplayer).

But u can access that DVDs directly over the device with mplayer, this has nothing to do with the filesystem. Just look to the Tooltypes and set the DVD-Device-Tooltype to "ide.device:<unit>". Should work fine. :)