Minor Email Issue

I seem to have a minor problem. When I open an email, could be from cnet, Webshots, my bank or just about any "company", if I left 'click' inside the read area, I can 'no longer' scroll up and down with the 'page up or the page down' keys. Nor can I scroll with the up & down arrow keys. I can scroll with the wheel on the mouse and I can also scroll up and down if I use the scroll bar on the right. If I don't click inside the read area, everything works fine. The odd thing is, on personal emails, everything works fine. If I click in the read area, the page up/down keys & the arrow keys continue to work. Is there some setting? Or is it that it has always been this way and I never noticed?

This happens using my Yahoo email account. Since I don't get much mail in my Outlook Express account, I haven't noticed this issue with that account. The email client is Outlook Express. I don't know too much about the Yahoo account except I think some people refer to it as 'web' based. I guess that means, I don't need to have OE working in order for Yahoo to work.

Dell dimension 2350, cable model, windows xp pro sp2, all updates. AVG free, Zone Alarm, Adaware 2007, Spybot, Spyware Blaster, regular scans with other online 'anti' stuff as well. All clean.

Thanks in advance for any suggestions,
Eddie