Error Console appears inadvertently
If a dialog box labeled "Error Console" appears while using Opera, the reason is most likely that Opera is reporting an error in one or more e-mail accounts set up in Opera's built-in e-mail client.
To prevent the console from opening automatically, look for mail related errors in the console dialog, and go to Tools > Mail and chat accounts to correct any errors in your mail accounts.
If you have any inactive mail accounts, you can set Opera to not check for new mail automatically:
Go to Tools > Mail and chat accounts to access the "Manage accounts" dialog
Select a mail account and click the "Edit" button
Select the "Incoming" tab in the account properties dialog
Disable the setting called "Check for new messages every # minutes"
It is also possible that the error console has been set to show on Web site errors. To prevent this from happening, follow these steps:
Click link to go to opera:config#Error Console Filter.
Click the "Default" button.
Click the "Save" button below.
http://www.opera.com/support/search/view/837