Sorry, but I really belive the problem is not related to the "cheap" memorex disc (RITEK-D01-01) vs the "better " Verbatim disc.
after a couple more coaster, the problem is always in the swtich between layer 0 and layer 1 of the disc. This makes me think that the problem is relate to the way ImgBurn do its job. maybe image burn tries to burn more sectors on layer 0 than there is on the disc... is that possible?