After a recent updated to MS Office 2011 my co-worker and I began experiencing the following issue.

Main Window of Outlook is up, previewing email. Clicking the red X in the top left it will close the window. We'll move on to a new task but when we wish to view the Outlook again clicking the Outlook icon will not bring up the Main Window.

Turning the program off and back on will bring back up the window but the moment you click close you can't bring the window back by clicking the Outlook icon from the dock.

After restarts of the program, restarts of the Mac Pro (Mid 2010, Yosemite 10.10.3), rebuild of the Identity and restoring our previous Identity (to keep our archives) we found that if Preferences > General > Hide On My Computer folders is checked we can open and close the window without issue. If we have it unchecked so we can see folders on the computer (where we maintain our email archive due to company size limits on email accounts) we can longer open and close the program freely.

Has anyone else experienced this issue?