Cannot start Microsoft Office Outlook. Cannot Open the Outlook Window

I encountered this problem when CEO of one of our client companies complained that he cannot work properly because of this. At first, I tried to do with System Restore because I thought that it will solve the issue. After restarting, it's still the same. I thought of reinstalling MS Office applications but I had a doubt that it will fix the problem. I search in Google for the possible solutions but most of them didn't work except for this one:

Steps:

1. Go to Start--Run

2. Type outlook.exe /resetnavpane

Then the Outlook will open just fine. 

This is what this /resetnavpane do: It clears and regenerates the Navigation Pane for the current profile. It's like deleting your profilename.xml in your user directory. This command applies to MS Outlook 2003, 2007 and 2010.