Out of the 30 you've burnt, have they all been from that exact same spindle of 'MCC 03RG20' discs?
If the drive has a write strategy for 'MCC 03RG20' in the firmware (which I'm positive it will have), it'll be geared for Verbatim MCC 03RG20 discs.
If yours are by some other brand then they might not be exactly equal and so strategy will be wrong - hence why it can't burn them.
All you can do is try some other discs.
As recommended above, buy some Verbatim DVD+R's or some Taiyo Yuden DVD-R's (I like the 8x TYG02 ones myself).