DVD verifcation error with Nero

When ever I burn something with Nero and verify, around 80% of the time it’ll tell me that a file fails (CRC error) and sure enough the file is corrupt when I try to access it on the DVD. I don’t think its under buffered because I have a gig of ram on my cpu and I run nothing while burning, not even internet explorer, also buffer levels are at 90%+ throughout. Is this a problem with Nero? Or a problem with my burner? I have a Samsung TS-H552b with TS-08 firmware.
Also can someone tell me what DVD High Compatiability mode is? It says that at least 1GB of space will be written, does that mean I can only burn 4.5gb minus 1gb worth of data on a dvd without screwing up?

Appreciate any help =)