Memorex is not the best media you can buy. I had a 50 cake Memorex DVD-R once. I tossed half of them to the bin (burning errors) and the other half gave me constant reading problems. I ended up burning all that stuff again on Verbatim DVD-R which solved those problems.
Get high quality media like Verbatim or Tayio Yuden and burn 4x - 8x. Slowest speed is not necessarily the best, depending on burner and media used. I always burn with 8x speed using Verbatim DVD-R and Nero or ImgBurn, which gives me the best results.
You can check the quality of your burns with Nero Drive Speed, or similar programms. Should give you a pretty good idea about why your discs don't work.
The PS2 can be pretty picky about discs depending on model and laser installed. My v12 is probably one of the worst, it burned two lasers already. Glad I got my HDCombo .
best regards Jones23