Operating System: FC13 Beta x86_64
Zdesktop: Beta 2.0

Steps to replicate

1. View Reading Pane At The Bottom
2. Close Zimbra desktop
3. Open Zimbra desktop

You will now see two columns for Account. Close and open zimbra again, and you'll have four Account columns. Switch to Reading Pane On The Right and back to Reading Pane At The Bottom, and the Account columns reset back to one.