[arch-general] Intel SNA artifacts in Firefox

Since the xf86-video-intel update that enabled SNA by default, I've noticed that some areas of some web pages (mostly flat backgrounds) in Firefox suffer from heavy graphical corruption, as if those areas are being used as rendering buffers elsewhere: bits of web pages from other tabs, etc... It goes away when I scroll the page. It happens regularly, every couple of minutes or more. This is on a Dell Latitude E5520 (Sandybridge i5) with KDE. I'm wondering if anyone else is seeing this? Paul