I purchased a 15 pack of Maxell DVD-R 8x at Walmart. I opened the cakebox and burned the first DVD. The first DVD was a Maxell 8x DVD-. However the rest of the DVD-R in the cakebox are Memorex "cool colors" 8x DVDs. The packaging was factory sealed plastic, no evidence of tampering. Has anyone ever seen such a thing? The Memorex will not work in my machine (Sony DRU 510) - they spec out as Riteks.