Toast 10 ,Error:-50 (Burning Dual Layer) Urgent

Dear i have been trying to burn 3-hour footage on DVD+RDL ,using Toast 10,I have build everything in DVD Studio pro 4 , and i did set up a breaking point , i built format , Their no problem reported i test it using DVD player built in Mac , Everything was perfect , Its just Burning DVD- DL which is causing me problem , I have new Intel Mac pro with ability of burning DVD-(+/-) DL , i have no problem Burning normal DVD (5) ,but i have getting this message :

Interface Error;-50
The Connection is not stable

another one

The drive reported an error
Sense Key=MEDIUM ERROR
Sense Code=0x02
NO SEEK COMPLETE

CAN ANY HELP ME PLEASE

Thank you