Considering how difficult Microsoft makes submitting bug reports about Office I have given up on being helpful to them and thought I'd try to be helpful to other users.
I had a problem with my Reading Pane being blank when I used the arrow keys or space bar to move from message to message in Outlook 2010. After trying the usual options (disable add-ins, safe mode) I discovered the issue.
If you enable the feature "Don't automatically expand conversations when using the keyboard to change messages" and are in Conversation View, then using the arrow keys or the space bar to move from message to message causes the Reading Pane to be blank or empty. Nothing shows up even if you move it or turn it off and on again until you use the mouse to click on a message. Apparently that option really means "Don't expand conversations or display messages in the Reading Pane when using the keyboard to change messages".
Network and Systems Manager