Try to delete some files and use the CD-R burn again... I have same epxerience before.. being the CD-R NOT 100% full 650MB, and for the disk... 650MB is 650,000kb... = 1MB = 1,024 kb = 634MB... and reserver some space load in/out... you may only can burn 620MB data...
Hope this can help.... I think at least you know your CD-R is WORK