DVD's are weird in terms of their formatting and the technology is changing very fast. To answer your second question, you need to figure out what kind of DVD writer you have. In CD's, its enough to know that it is a CD R, but on DVD's you have to know if it is CD+R or CD-R. Usually, whatever it burns is the only kind of DVD's it will read even if there is data already on them. It's possible that you have the wrong format. I think most of the new ones are DVD+/-R (both) but I've had this issue with mine because it is a "-" only. As far as I know, it doesn't matter if they are RW or just R as long as the + and - are right. As far as dual layer DVD's, I know they exist and require special burners to utilize the dual layers, but I don't know anything about compatibility with single layer burners or readers.
Now, to the first problem... when you say you are trying to pull images from DVD's, you are trying to get stills from movies? And these movies were created to be played in a standard DVD player for viewing on the TV? I know that, with my dell using windows movie maker, I can capture stills from .mpeg's and a lot of other file formats if they are saved as files on a data disc. Whether or not you have this program is another question, but I think it came as part of the package that I got with the DVD player. However, it sounds like your problem is in getting images from a movie formatted to be played on the TV through a regular old DVD player (and that I don't know how to do). The fact that you can't play the DVD on your computer sounds like the formatting problem that I talked about above.
If you have the original digital video tapes and a camera that will play them (at least I assume this is what the DVD's were made from...depending on the format I may have access to one of these) I have a firewire connection that you can download the videos into files and then capture pics from them, but this would take a hell of a lot of time as you can only download the videos at the speed that they play and the pictures don't end up being the highest quality unless they were taken with a really good video camera to begin with (so time intensive with little payout in the end). I mess with a lot of videos because I study how 2 year olds learn from TV and not only do we have to make and edit videos for our experiments, but we also have to score the videos for certain behaviors after the experiments are run. Any shortcuts help speed this process, but truth be told there don't seem to be many. If I can be of any help with this, you know how to get a hold of me. If I don't know the answer, I know a lot of other people that probably would.
