Try burning at 6x or 8x with a brand new blank disc. You might also want to try cleaning the drive with a lens cleaning disc. If none of that solves your problem then you'll need to get a new burner (it's cheaper than a 10-pack of Verbatim blanks).
The thing is, i used to always burn with 2,4 or AWS, nevveer had this problem before, gonna put up a error message.
EDIT!!! I just tried with a brand new DVD and at 50% it came up some spindle servo error, pic in a sec
PIC! http://img22.imageshack.us/img22/6521/10849756.jpg
Please, anyone out there that can help me?