The +/-R refers to the way the information is actually physically stored on the DVD, not the structure of the files themselves. If you get a PC, simply rip the files on your
DVDs to a hard drive, and then re-burn from the hard drive to a + or -R as desired. I've done this may times.
Also the Liteon uses the DVD VR format which differs slightly from the DVD Video format, but most readers but not all can accomodate this. This might be another reason why the Apex fails?
After much trial and error, I now record all my programs (using a stereo VCR tuner) via SCART to DVD+RW disks (no need to finalise), and then transfer to a PC (Nero Recode, DVD Decrypter are two good packages), and copy to DVD + or - Rs as I wish.
You can copy any DVD directly to another DVD+/-R using a simpler burning program (e.g. basic Nero) if you wish, and do not intend to do any editing of the disk (simply use the Liteon menus to rename menus etc if desired). This works but the copy is still in DVD VR format though.