I've had wp running fine for 6 months then decided to create some pages. When the pages are displayed, the sidebar is pushed to the right.
What I've discovered is that an extraneous P tag appears on the "page" pages, See http://www.oldguy.us/public/ptag.gif for a screen capture using a FF extension that shows block level elements.
Don't know where the P tag is coming from. It's not in my code. See http://www.oldguy.us/public/page.txt for a list of my page.php file and the subscribe post.
I wouldn't think the P tag would cause the margin shift but it's the only anomoly I see.