Theme not displaying correctly in Internet Explorer 8

I’m loving the DW Minion theme on my blog, but have just tested it in Internet Explorer 8 and it seems to be using the mobile layout.  Here’s a link to the blog:http://blog.derekjwhitten.id.au/ I haven’t really modified the theme, except to change some colours and fonts. In case I had broken something, I went to the Appearance page in the Admin panel and chose the live preview but I’m getting the same results. Are there any known issues, or is anyone able to see the issue in my CSS? Thanks in advance for any inputs.