My 3500 won't burn dvd-r



I can’t get my 3500 to burn any dvd-r. It is located in a firewire external case connected to my laptop running xp pro. I am using the original firmware. I have tried Verbatim and fujifilm discs. I have no problem burning dvd+r or dvd-rw. When I use nero I get a “no seek complete” error. I have also tried Record Now and it gave an error as well. Anyone have any ideas?