I upgraded to 2.5.1 using the upgrade plug-in. All seemed to go well. I reactivated my previous theme and made a new post. So far so good.
Then I went to my website and clicked on the category, page and post-title permalinks as well as the "next page" link at the bottom of my homepage. Clicked on photos too. Nothing works. My browser just keeps saying "Page not found..."
I've checked my options in the control panel. They're all set the way they were prior to the upgrade, including the permalink generation.
What did I do wrong? My URL is http://www.mimlay.com. The theme is Apple-10.