CentOS - Mar 2011 - Problem burning dvd's

I have a question on burning dvd iso's, using k3b.
I have a sony dvd rw, and I've burned cd's with now problem, including
iso's. The problem I'm having is, when I burn a dvd iso, k3b says
it's a
success, but then when I re-insert the disk, the drive tries to read the
disk, but the read/write light just stays on, and the drive can't access
the disk. Am I leaving a step out, or something? I burn cd iso's all the
time. 

Thanks

Jim