Ps2 back-up keeps loading.

I'm using the fat ps2 with swap magic, and flip top and i've managed to boot up Swap magic correctly, but the problem is the back-up. I'm trying to play Valkyrie Profile 2, and the game will load, but every two seconds it's says "reading disc", and alot of the dialog skips.

I used a Memorex 16x+r to burn, with Imgburn. It there something wrong with the brand of disc, or was the iso burned incorrectly?

Also I tried to burn Xenosaga I to a JVC dual layered DVD-RDL disc and that just boots as "not a valid PS2 disc". Did I use the wrong disc for that as well?

I even tried burning Codebreaker iso 9.2, and that won't even boot...just a black screen. The things is all of these disc (except Xenosaga) work on my Pcsx2. I'm wasting alot of discs...I'm really frustrated.