It may be a good idea to scan your DVDs and see how their quality is. As you don't own a LiteOn drive, you can't use the magnificant KProbe. You can use either the Nero CD/DVD speed tool (not a good testing utility, but it always reveals some info) or the somewhat better DVDInfoPro to see how your discs perform in your computer.
If their perfomance isn't that good, you most likely found the reason why the PS/2 doesn't like the burned discs.
Another thing that could be the case, is that the PS/2 just might not like certain media.... supported or not!