Way back in the day, there were gold CDs, blue CDs, and silver CDs... and each manufacturer has some limited ability to work with each kind. Are these rejected media commercial DVDs you are using (should be silver in color), or ones you have burned yourself? Any surface scratching (some drives are more tolerant than others)? If you are burning your own in another machine, make sure your slot load drive is compatible with the type of media you are using. Sometimes drives only like DASH (DVD-R/W) vs PLUS (DVD+R/W) media. Sometimes the ReWriteable media is not tolerated.