Logic 7

I'm also getting this message periodically. I used to be able to use imation discs my wife bought for me a couple years ago but they dont show up anymore and now I use Tayo Yudens and sometimes I have to load the disc several times before I can burn to it. I use DVD-Rs by the way ?????????????

I have used Verbatim DVD-R discs for a while and now when I put one in and try to burn I get medium not found. When I use Taiyo Yuden it recognizes them every time. but I would like to use up the verbatims. Can anyone help?