Occaisional Issue with Outlook Attachment Preview Not Displaying

One of our users is frequently experiencing Outlook failing to display the attachment preview.  Roughly 15-30% of the time a blank pane is displayed when that attachment preview is invoked.  Sometimes that same message / attachment combo could be selected within a few minutes of each other - the first time it might not work, while the next time it could well display correctly. This began ~3 weeks ago, and we have been unable to discover anything that had changed to cause this. Has anyone experienced something similar, or have a suggestion as to what could be causing this issue?