Outlook 2003 Send/Recieve

I use Outlook 2003 with POP3 setup. Until yesterday the option to send /receive message every 5 minutes was not checked and was working great. Today the option is still unchecked but Outlook sends/receives message every minute. I have tried to check it and then uncheck it but to no avail. Any one knows why this behavior. No settings have been changed in Outlook at all. I’m very frustrated. Thanks