HELP PLEASE!!! DVD-Rs that I made on a recorder will not play on my Inspiron 1150

I recently purchased a Panasonic DVD Recorder and have been putting some old VHS onto DVD.  It's worked fine and all of them play on the recorder.  The problem is when I try to play them on my laptop.  Sometimes they work fine, but often PowerDVD will lock up after about 5 minutes or if I try to FF.  I've tried two other players and have the same problem.  Panasonic suggested I switch brands of DVD-Rs and I tried that but it didn't help.  I live overseas and I'm running out of time to finish this project.  Help, please!