One thing you should be aware of. Memorex doesn't make thier own media (neither do most of the brands out thier). Use this program to read the media code off your blank disks, it identifies the true manufacture.
Memorex has a bad reputation for using whatever they can get cheapest so it could be the best in the world or the crappiest or anywhere inbetween so it is a very unreliable brand to buy. The memorex 16x+r hasn't been out that long and there are already four diffrent medias reported that they have used. You can go here and enter a brand to see what media codes it is liklly to be
Also, like zazonz said, even if media is good quality, sometimes a burner just doesn't like a certain media. Scan the media code off your memorex. If they are not mcc004, then I sugest you try some verbatium 16x+r if you want to try 16x media. It is good quality and works well with most drives. That why you want to look at the media code though. Your memorex might be mcc004, in which case, you already know the verbatium wont work well as it is mcc004.