CSS issue with sidebar in page template

I’ve only tried this in Firefox 3.5 but I’m sure it’s similar elsewhere. I’m currently wrapping up design on a template and my problem is the sidebar div is collapsing underneath the .widecolumn class. I’ve tried all sorts of things including changing margins, padding, positioning, etc and nothing seems to click. Anyone know how to correct this?

https://76.12.165.13/?p=1