Hey, thanks for the interest and info. If nothing else I am learning a lot. However, I am also getting deeper into mystery, and at the risk of turning people off, I'm going to lay out what happened and what I'm doing, hoping for any assistance, making me a smarter person. Here goes:
Here's an update: I bought Wondershare's Data Recovery for Mac. The company gave me a nice discount after I wrote to their support explaing what happened and how I'm fairly sure it was caused by my use of their Video Converter Ultimate, and that as a customer of some other apps of theirs, maybe they could cut me a deal - which they did. Nice.
So I used it and am using it.
I'm going to put in here a couple of things that I would love any help understanding.
1) The recovery program found 563 GB's of data. When I ran it I specified "deep scan;" video files only, and doing so on one targeted volume on a partitioned internal hard drive. (It's a 1 TB drive, 2 partitions, 400GB on one and 600 on the other. It's the 600 GB volume that this happened with.)
2) I use this volume for all my video files. Home made, made by friends, downloaded, tv series, movies, You Tube vids. A mix of various video file types. It was not full. It had approx 300 GB on it at the time.
3) When it happened, I was trying to copy the contents of a DVD (my own, my footage, edited and created using a combination of iMovie and Quicktime. I'd lost all my original material and the only copy I had of my original footage, with edits, was on the one DVD I had burned several years ago. I was trying to capture it all so I could re-import it into iMovie and work on it new.
4) I started with Handbrake but ran into several problems. Had to download newer VLC as well as "libdvdcss pkg" plus switching between 32 and 64 bit versions. It still would not work so I gave up and tried my Wondershare Vid Convert Ult, using it's copy and burn options.
5) I don't know if this caused it but during the copy stage, I walked away to give it time to work, and soon afterwards heard my Mac restart. I could not find anything copied, so I gave it another go. It did the same thing again - started copying, I left it alone, it restarted my Mac, nothing copied, not that I could find.
6) Looking for any copied material, I went to the destination folder (on the 600 GB partition/volume) and discovered that the entire volume was empty. The other partition was intact but all the video files I had on that volume were gone.
7) I went hunting everywhere but could not find anything. Nothing in the trash either. Ran all the usual utilities, including booting from my original install DVD and using Disk Utility to repair everything.
Searching the net for any clues, help, explanations, I came across a You Tube post that explained the use of Linux Mint. Which is what brought me here. I booted from the CD I made after downloading "linuxmint-12-gnome-cd-nocodecs-32bit.iso" I was amazed that it worked and what it could do. But, alas, it only showed the volume in question as empty.
9) If trash showed nothing, all internal drives showed no signs of all the missing data, the volume in question showed 599 GB avai
and now my newly purchased WDataRec program has found and is recovering 563 GB's of video files...where was it??
10) Last note: the recovery program has provided me with 12 folders, each a different video file type. But all the files within have 8 digit numbers for titles, so I have no way of knowing what's what. As I methodically open each one to identify it, I find some are good but some are crazy corruptions - begins as one tv show, then turns intoa different one, and so on. Best I can figure is to view in a list and use file sizes as some indicator of what might be what.