[X4U] Disappearing Mailboxes

[wilkinw]

OSX4.9, MacBook Pro 2 gig memory.

So I launched my mail this morning and to my surprise all my  
mailboxes were gone except for in, sent trash. So like a good  
computer user of course I had a backup. Week old but none the less a  
backup. I copied my backup/Library/Mail folder to my Library Mail  
folder, launched mail, they were all there. Oh not really, they were  
there for about 3 seconds then all disappeared again. What they hey!  
So then I looked at my System Prefs/.mac and turned off any and all  
syncing, recopied the backup mail folder, same thing, they were there  
for a second or two then disappeared. Any help would be appreciated,  
Wayne.