Need help with DVDx

I'm trying to rip a few chapters of a NON-COPYRIGHTED dvd to my hard drive into mpeg format. However, if I try to set the output file's resolution higher than 320X240, the encoding process will end before it's finished and the program will give me a message that says something like "write buffer full." The higher the resolution I go, the sooner the encoding ends. What else do I need to adjust to be able to get a mpeg file with higher resoulution?
Thanks for any help in advance.

how much hdd space do you have?

and what program are you using?

Thanks for the response. I'm using DVDx 2.2. I've been ripping straight off the DVD.