I have a newish system running on WinXP SP2 and when I try to open the address book I am getting the error message "the address book failed to load. OE is incorrectly configured, please reinstall". Also most (but not all!) of my addresses have disappeared from the contacts window.
I also can't open any emails and get the message "There was an error opening the messgaes. An error has occured". Helpfull!
By using system restore I have discovered it is Windows Update KB911567 that is causing it. I have uninstalled and reinstalled OE but to no effect.