Change Focus to Inbox

I have outlook 2003 installed at home and in my office - same setup, same
exchange email account.

At home, when I pick a folder, like Inbox, the top mail item in the Inbox
list is highlighted in blue, because that's where the focus is. I can use my
up and down arrows to move the blue highlight, or I can just hit Enter to
read the mail.

In the office, when I pick a folder like Inbox, I get a grey highlight, and
the focus is not on the main Inbox window. In oder to read mail, I must first
click on one of the existing mail items to move focus to the Inbox window,
and then I can proceed to act on the mail.

I've compared the setup on both locations, and they seem the same. What can
I do to get the focus to move to the main window when I click on a folder in
the Navigation Pane?

Thanks