I too have had multiple problems playing large vob files ie timing out, not being able to fast forward past 4x, if you fast forward past the indicated time movie will restart etc etc.
After converting many movies for many days in heaps of converters and formats, I've come up with this workaround.
As vob aren't supported, my solution was to convert the dvd to another format. I wasn't too concerned about file size but I wanted to convert with the same quality as my vob files, and i wanted to do it rather quickly (as I was using dvdshrink to convert my dvd into 1 large vob in about 15 minutes give or take). I tried heaps of software converters and formats, the problems i had were in some instances although the file might have been smaller, i lost quality and most programs took hours to convert one movie, others were too damn hard to work out.
Now I know someone will have a better solution. but this is my solution, and its worked a treat for me. And its simple.
I have used a program call vob2mpg ver3 it's freeware. after using this i purchased the pro version for about 25 australian dollars. But anyway the freeware is fine. It converts the dvd disc in about the same time as dvdshrink (about 15 minutes give or take), the file size is the same as my vob and the quality is identical.
here's the link to the site:
www.svcd2dvd.com/VOB2MPG/default.aspxAnd yes they play perfectly on my wdtv.
PS: if the dvd you are trying to copy has copy protection, you will need to save to your hard drive with dvd shrink first (with no compression) then use vob2mpg.
Cheers after spending hours converting and trying different programs and formats this has been the easiest and simplest for me. So I hope this helps a few people out.
cheers steve