Newly ID’d by the nice folks at BugGuide. AKA Catocala amatrix. I posted this on BG.N back in August of 2010 and someone found it while cleaning up during the quiet winter season and gave me an ID.
This is a member of the Genus Catocala, which are known as underwings. When the forewings are spread to reveal the hindwings, we then see a wonderfully colorful display of red and black. I have yet to get a shot of the display.