I recently built a site for a client of mine. All was going good, the pages were working, I was adding plugins, everything. And then, I installed (and uninstalled, as it was too advanced) one called SEO ultimate. AFterward, my pages would not work, not even ones I created afterward. I get a 404 error everytime on every page, except on the homepage. I have no idea why it does this. I deactivated all of my plugins to no avail. I've even tried changing permalinks. Nothing works. Please help!