Disable AVG (right click tray icon Shut Down AVG Control Centre - you may have to also terminate the AVGSERV9.exe too) Open OE. If this works then you have too much stuff in your OE folders. AVG scans all folders when OE is opened - to many big attachments can cause AVG to hang.
Clear out as many e-mails as you can. If you have attachments you wish to keep save the attachments to the hard drive and delete the messages. Delete all deleted items. Compact the folders (Tools, Options, Maintenance, Clean Up Now, Compact Now)