Not sure about Realplayer, that could be a case of not having a certain codec. The Toshiba DVD player may be bit more problem. I have found that a JVC player with DVD-Audio capability that cost >$100 about 3 years ago will not play burned dvd's but a JVC that cost $43 and a Proton that cost $35, both will play burned dvd's fine without regard to the disk being + or - R, PAL or NTSC, or what brand or manufacturer made the dvd. CompUSA, Walmart, Circuit City have a Phillips player for $70 (I think its model number is 639 or similiar) that supposedly will play anything- Divx, Mpeg4, CVD, mp3, etc.
I'm finding out the cheaper players work better for burned disks because they are manufactured to be sold all over the world unlike the $200 players which are manufactured specifically for the North American or European markets.