Position discrepancy between blog and pages

My blog layout is eight pixels to the left of where my page layouts are, so when you jump from one to the other, there is a noticeable shift. This is true no matter what theme I use, including the default one, so it’s not my markup that’s causing it. I also reinstalled WordPress 2.9.1 to replace any files I may have inadvertently tampered with. No luck. This is strange. Anyone have an idea about what might be going on?