Very odd one here.
Rendering at high quality, exterior sun only, 150 DPI and the image is about 9' tall x5' wide. Everything goes great until it hits 26%. Then the bar goes full on 100% but the image is only 26% rendered.
Ends up looking like the image I attached.
I have a 2gb video card, 4.1Ghz overclocked processor and about 8GB of RAM. Perhaps I havn't allocated enough memory to render an image of this size?