Did you try logging the connection and investigating to see if a certain message is causing the crash?
Try renaming operaprefs.ini in the preferences folder so Opera creates a new one. In the sessions folder, delete autosave.win.
I'd also test if your anti-virus (especially its email scanner) is causing Opera to mess up.
Might want to check your file system for corruption. chkdsk /r on the command line (run as administrator) and enable a scan on reboot (will take a long time).