With older set top players, lower burn speeds is better. I always burn at 4x no matter what. Just the way I am.

Media brand can be a factor as the quality varies from brand to brand and within the brand itself.

Could be a +R or -R or RW issue as well.

What media and type are you using?

Here is a good site to tell what media type a player accepts:

http://www.videohelp.com/dvdplayers