Search broken on subpages

I don’t know what I did, but my search isn’t working on any page other than the main page.

My site is http://www.variablemarkup.com.

If I search on anything on the home page, I get a url like

http://www.variablemarkup.com/?s=stores

But if I search on another page, I get a url like

http://www.variablemarkup.com/2007/09/05/implementing-buy-online-pick-up-in-store/?s=store

I think my problem is that it maintains the URL instead of clearing it out.

I’m using All in one SEO pack which rewrites the url. Could this be causing it?

I’ve mucked with a couple pages trying to do other things, but I have no clue when it stopped working.

Any guesses on what it might be?

Thanks!