DVD Recording is driving me crazy - help!

[RenaissanceGurl]

I'm trying to convert VHS tapes to DVD. I have been able to copy some of them but I have had the DVD recorder freeze up quite a bit with the message "Recording is closing. Please wait a moment." (This should show up when I choose to stop.) I have to unplug the recorder to be able to proceed. I have bought and returned (4) Sanyo DRW-1000's from Wal-Mart and (2) Zenith XBR413's from Best Buy. I've spoken to Sanyo and Zenith. They both assure me that it's the machine. It's hard to believe that all of these machines are defective. I'm using Sony -RW's. If anyone has had experience with this and any advice, I would be truly grateful. Thanks.