You are proobably not doing anything wrong. It is more likely that your DVD Players have a compatibility issue with DVD+R media. You can check this out at http://www.videohelp.com/dvdplayers.
As a general rule you will have fewer compatibility issues with DVD-R, but you can check this at the same site.
COMPAQ something or other with 500Gb Boot Disk, 1Tb external Firewire Disk, 4Gb Memory and a super duper sound card, 19" TFT Monitor etc etc etc
Sony TRV33e : Sony TRV310e : Canon XM2
Sony Vegas Studio editions to v11
Remember, there is always more to learn than there is to teach.