> I am running PMail 4.52 on Windows Vista. It hung this morning.  When I re-started it gave me the message that the mailbox is already being
> accessed. When I override it finds all the folders but then stops working with a notice saying that I can look for a solution on the
> internet or close the program. In either case it closes the program.
>
> I tried downloading version 4.52 again and installing. I did an update rather than a new installation.  The problem persists.  If I do a new
> installation, how do I make sure that I get back my mail and my folder structure? (I don't want to do a "new" installation and lose my
> current mail, dates, or folders.)

Move all of the *.CNM files out of the new mail directory and try again.  It should now open normally.  You can then put the messages back one at a time until you find the problem message.  

Also you might need the zero-byte CNM fix.

This zero byte file is causing Spamhalter to crash and the OS also takes down Pegasus Mail.  You need to upgrade Spamhalter.

Spamhalter Zero Byte File Crash Fix
http://community.pmail.com/files/folders/community_add-ons_for_pegasus_mail/entry23105.aspx

I am running PMail 4.52 on Windows Vista. It hung this morning.  When I re-started it gave me the message that the mailbox is already being accessed. When I override it finds all the folders but then stops working with a notice saying that I can look for a solution on the internet or close the program. In either case it closes the program.  I tried downloading version 4.52 again and installing. I did an update rather than a new installation.  The problem persists.  If I do a new installation, how do I make sure that I get back my mail and my folder structure? (I don't want to do a "new" installation and lose my current mail, dates, or folders.)

I have found the solution to this problem.  I found a 0-byte CNM file and removed it.  PMail opened correctly.  Apologies for posting my question without looking deeper into previous messages on the forum.