Tested the ribbon preview button in the Firefox browser first because most often bugs of this nature will perform correctly in this browser as opposed to IE.
Once testing in Firefox, I found that it did not work correctly in Firefox 9.0. I disabled the built-in Firefox popup blocker in the browser and retested to find that the preview window did open in a new tab. I'm considering this problem fixed in Firefox and user error.
On to IE, I immediately disabled the browser popup blocker, only to find that the Preview window performed as this bug describes (not doing anything). The HTML and CSS for the button is the exact same as shown in Firefox using the developer toolbar.
On the out of box web site, the Preview button performs correctly as one would intend the button to. The underlying HTML is the same as the HTML that's being shown on the production web site on both Firefox and IE.
I tested on the Mac and it works correctly in Safari.
I tested in compatibility mode in IE only to still see the problem.
I'm not sure where else to go for tasks with testing this problem.
This appears to be a Sharepoint bug, and I suggest moving to the Known Issues area and documenting that it can be fixed in Firefox by disabling the built in popup blocker.