Rounded borders don't show up most of the time in Opera 8.0

I've noticed a weird issue in Opera 8.0 where the rounded borders don't actually show up most of the time. They show up in the Community page, but as soon as I click on one of the links there and hit "Back", the borders disappear, leaving me with unbordered plain rectangular boxes. Subsequently clicking on a link displays the borders again right before it loads up the new page. I'm not seeing any rounded borders in the forums at all, and various other areas on the site.

edit: it seems the rounded borders are showing up when I create a new topic or edit my post, and they also show up when viewing threads that I started. Hmm, even that's intermittent.