When you run OE you get "An error occured whilst launching, the end of file was reached"
Close OE
Run OE again holding down the "Alt" key.
It will then prompt to compact the database, click "Yes".
If it is unable to do so then it will prompt to do a complex rebuild.
WARINING: - If you click "Yes" to a complex rebuild OE will rebuild your mailbox's, back up the old mail to databases and leave you with a blank OE (no messages).
You will then need to re-import all the messages from the database back-up files.