Has this been resolved yet? I downloaded the trial version last night and I'm having a similar problem.
I tried using a drive that had some data on it, but kept getting this message. I tried chkdsk on it and it tried to fix it. One directory seemed to work after that, but the others failed.
I removed it from the pool, reformatted it, and added it back as an new and completely empty drive.
I created a few top level directories on it. It seemed to take a very long time to create them. I was beginning to think the process was hanging.
I started copying files. The first batch was about 170GB. These seemed to copy fine. I checked a few of them and they were all accessible and correct.
I started the next copy which was about 650GB and went to bed. When I woke up, it. appeared that nothing had been copied and it was displaying the error saying "A device was specified that does not exist".
I tried copying one of the files from that batch again and was told that the file existed and asked if I wanted to replace it. When I said YES I again received the message about the device not existing.