Error -40 is a positioning error (tried to position before start of file).
This might indicate file system corruption. Try running Apple's Disk
Utility: First Aid and repairing the disk till it shows clean.
If you are still having problems report back with what version of Entourage
you are...
First try this easy fix.
1) Quit Entourage.
2) Move the Microsoft User Data folder to the desktop
3) Open Entourage and it will create a new Microsoft User Data folder with
an empty Main Identity
4) Drag from the MUD folder on the desktop, your Main Identity replacing the
current blank...