Outlook – Getting back to the same instance of Outlook 2007

My problem is that I assigned a shortcut to Outlook like this: "C:\Program Files\Microsoft Office\Office12\OUTLOOK.EXE" and this worked fine and just like I wanted it to: when pressing the key I came back to this oneandonly instance of Outlook all the time.

Then something happened and I lost this behavior with the shortcut key, so now when I press the shortcut key it starts a new instance all the time…

I have tried with various switches my best so far is: "C:\Program Files\Microsoft Office\Office12\OUTLOOK.EXE" /edit which takes me back but this prompts me that the switch is invalid all the time.

So is there a switch to get me to the state where I just get back to Outlook, without prompts?