That's cos the standalone players compensate for some DVD errors I imagine cos they know that discs get dirty or scratched.
Your DVD drive in the PC looks for perfect data off the disc, what it's saying is that your data, just burnt is NOT perfect.
You have quoted Sony & Memorex as the brand but they don't make the actual dye on the disc. This varies a lot between manufacturers, the best is probably those made by Verbatim and Taiyo Yuden with some of the worst being made by CMC MAG.
Take a look at a log from ImgBurn and see what dye your discs are using then look at the Media/Drives forum (link in my signature) and see some tests on most commonly used media, if yours is in there take a look at the scans etc compared to Verb and Taiyo Yuden dye.
If you post a copy of your log we can check the dye manufacturer for you