hELP - Copying DVD Sonic

New user of Dimension 8400 series, trying to copy a home movie DVD. I have followed instructions in 'user manual' and used 'Sonic Record Now' to get 'exact' copy of DVD. DVD copied succesfully and DVD ejected. Then prompted to insert disc and have inserted DVD-R to make copy. Disk drive keeps ejecting disk with message 'please insert a blank or re-writable DVD into the Phillips DVD+RW 9 (D:) Drive'. I keep inserting disk and pressing ok but message above is repeated. I have tried several new TDK DVD-R disks, all new and sealed. Can you help???????????