sounds like the next step is to try better media then. i don't know where you're located but the bargain basement subforum always posts the best deals. quality stuff costs exactly the same as the "cheap stuff" you just have to know what to look for.
out of curiousity, have you burned the CMC MAG AE1 on this drive before?
actually, nm...you prob wouldn't know if right now is your first experience with media codes. for future reference, some Brands of media change manufacturers often and without warning. If you've had goo dluck with the "same" media in the past, it's possible that they've changed manufacturers and their current media is sub-par. part of getting good media is taking the guess work out of what's inside the spindle. the Bargain Basement and Blank Media forums should go a long way in helping you sort of media issues.
also, check the Phillips optical Drive subforum to see if anyone has the same drive as you and what media they successfully use. everyone will have different experiences, but maybe you can at least get some leads on what "plays well" with your drive.