I'm not sure what your Philips drive is, but I think I know what the problem (and solution) may be.
If the disc does mount, and all of the normal files (VIDEO_TS folder at the top level) show up, then there was probably a problem with how it was burned.
But, you still should be able play the discs. Try this: After you've put the disc in, open Apple's DVD Player, go to "File>Open VIDEO_TS Folder..." and then select the VIDEO_TS folder at the top level of the DVD. Then press Play, and it should work.
Fixing the problem in the future: If you're using Toast, make sure you choose "DVD" as the format when you burn. If you don't have Toast, you can use a freeware app called DVD Imager (
http://lonestar.utsa.edu/llee/applescript/dvdimager.html) to create a burnable image file. In both cases, make sure the title of your disc is all caps (with no spaces or weird characters), and the top level contains your "VIDEO_TS" folder and an empty folder named "AUDIO_TS"
Hope this helps.