[Off Topic] Burning DVDs

[Jonathan Ryshpan]

I'm trying to burn a DVD for installing FC3.  I've downloaded
FC3-i386-DVD.iso using BitTorrent; it checks OK comparing the
accompanying md5 file MD5SUM.

I've tried to burn a DVD using k3b; so far I've made 4 such DVDs. 
Unfortunately, these DVDs are all bad.  K3b indicates a comparison
failure, and invoking "linux mediacheck" on booting from the DVD
indicates the same thing.  Some of the DVDs won't boot at all.

The CD/DVD drive is a LITE-ON DVDRW SOHW-1633S.  The DVD blanks are
Memorex 4X DVD-R.  K3b was running in "Auto" speed burning some DVDs and
in "4x" speed burning others.

Does anyone know what the problem might be?  Any idea on how to cure
it?  Different brand of DVD blanks?  Clean the drive?  Whatever?