I open my outlook and it defaults to showing an older email in the reading pane. Say I have 3 new emails today and 3 emails from yesterday.
I click on one of the new emails, it shows up in the reading window for 1 second, then the highlight bar switches to an older email from yesterday, for example, and displays it in the reading window.
I can click again, and again on the new email, but it just switched back to the older one.

I have run malware and nod32 scans, nothing found.