I believe I figured out what was going on. A detail I failed to mention was that as I moved the messages I also deleted the old folder because it was no longer used. I think I may have inadvertantly deleted the new folder while attempting to delete the old one. As you suggested I stopped my Trend Micro AV and tried moving messages and it worked fine. At the same time I decided to not delete the old folder until later. I moved messages from many folders with no consequence. Even after deleting the old folders later there was still no problem. I restarted the AV and still had no problems.

I would recommend to the programmers of Pegasus to put the name of the folder in the caution about deleting a folder so the user knows exactly which folder they are deleting. Thank you very much for your support and input.

Wendel 

I created an archive mailbox to allow archiving of older emails. I created folders and subfolders and moved many messages. Today I decided to move more messages. I do some eBay auctions. I have many small folders within a larger "Auctions" folder and decided to combine many of those in the archive into one "Selling" folder in the archive. I moved the messages from 5 to 8 small folders to the "Selling" folder and when I tried moving more messages the "Selling" folder was gone. I closed and reopened Pegasus hoping the folder would reappear but it did not. I recreated the "Selling" folder and tried moving a few more messages. Everything seemed OK and I closed and opened Pegaus and it was still there. I watched the folder on the hard drive where the archive is located and the folder with the most recent time was there and had grown as I added messages. I went back to Pegasus and moved a few more messages from a few more folders and it disappeared again. The folder was gone from Pegasus and from the hard drive, as though it has never existed. There is no error message or other indication of a problem.

Has anyone ever experienced this before? What can I do? 

[quote user="WendelB"]

I created an archive mailbox to allow archiving of older emails. I created folders and subfolders and moved many messages. Today I decided to move more messages. I do some eBay auctions. I have many small folders within a larger "Auctions" folder and decided to combine many of those in the archive into one "Selling" folder in the archive. I moved the messages from 5 to 8 small folders to the "Selling" folder and when I tried moving more messages the "Selling" folder was gone. I closed and reopened Pegasus hoping the folder would reappear but it did not. I recreated the "Selling" folder and tried moving a few more messages. Everything seemed OK and I closed and opened Pegaus and it was still there. I watched the folder on the hard drive where the archive is located and the folder with the most recent time was there and had grown as I added messages. I went back to Pegasus and moved a few more messages from a few more folders and it disappeared again. The folder was gone from Pegasus and from the hard drive, as though it has never existed. There is no error message or other indication of a problem.

Has anyone ever experienced this before? What can I do? 

The only time I have seen a whole folder disappear from the hard drive is when the a-v software found what it thought was a virus in the folder and then deleted the whole folder.  This one is quite common when your a-v software is set to use auto protect on mail folders.