Very very weird problem with DC backup's

[Vader]

Hi. I have a very weird problem with backups for the DC. I have a few games that i have been playing for a month or so and now when i put them in my DC they don't want to boot up. What is the problem. I made the backups at x1 speed on a Sony writer using Memorex cd's and the DJ vers.3 program. Do you think the cd's aren't good. I looked at all the cd's and they have no scratch on them. Do you think that the problem may be the color of the surface of the cd. The Memorex cd's have a light light green color to it. Should i try the black cd's that they sell. All original DC games that i have do work properly and i have no problems with other backup games ( up to now ). Thank you.