I hated Videora. Quite a few people have had the issue with no audio. Apparently there is some audio setting within Videora which you have to change. I changed converters & had no problems. Within the thread below is a link to the 3GP converter. If you'd like to try it, follow 1337's instructions
http://www.gnutellaforums.com/showth...=&pagenumber=1

As for why you can't delete, I'm not sure. Just highlighting the file & pressing "delete" on the keyboard usually works for iTunes (you'll have to delete the videos in iTunes & then update your iPod. The iPod itself doesn't have a delete function).