This is the first thing you need to learn, reguardless of your problem (and it may be the cause of your problem). Memorex doesn't actually manufacture any media. Memorex is infact, the worst total media slut of all time. They will buy any media that they can get cheap. It is quite normal for various brands to use other peoples media.
Take any disk you have, blank or burned, drop it in any of your computer drives. run dvd identifier
it will give a manufacture id etc.
Your tdk is most liklly ttho2, your memorex might be cmcmagam3 or ritekf1. These id's tell what the disk actually is (who made it, what it is). the brand is insignificant. It tells nothing.
download cdspeed (its free), and it will tell you what your drive is. beyond that, all I can sugest, is if you want to use 16x media, use verbatim 16x+r (which will carry a media code of mcc004). There are others that are mcc004, like office max 16x+r, but not all office max 16x+r is mcc004. There are certain markings on the pack to look for.
If we knew what your drive was, we could tell you if it could scan (many burners can scan a disk that you have already burned and give an error report of sorts. You can get a pretty acurate idea how well the disk burned, and believe it or not, it varies from exceptional to no way in hell one bit of that disk could be readable. Even with good media, your drive has to support it and be able to burn it well.