I successfully switched the primary/secondary around with a little bit of judicious editing of the /etc/X11/xorg.conf, but still no second active monitor. Apparently the ATI driver's programmatic editing of xorg.conf really likes the idea of working with a single video card with dual plugs, either dual analog, analog/digital, or digital/digital, or a single adaptor with dual screens, as in a laptop. Maybe that *is* the issue, although I was under the impressing that Xorg could handle both drivers without too much difficulty. It's not like the conf file is complicated or anything.
Anyway it slices, I have *not* figured out how to get it to work right, although I'm thoroughly enjoying using my considerably crappier Intel on-board video until I go fork up for a dual-head card. Bah! I don't really expect X11 to be completely as easy as windoze, but it's decidedly proof-positive that *nix is used for mostly server applications because the UI isn't really any further ahead today than it was 8 years ago. Maybe I should go install Mandrake if I want a workstation/UI centric *nix on my workstation.
For what it's worth (and I know this won't help your current situation) I've had HORRIBLE experiences with ATI support on linux, even with their binary drivers. Nvidia has always been more reliable for me, and I've got dualhead running just fine with an nvidia card and 2 widescreen lcd's.