All links broken

Today I activated SEO by SQUIRRLY and SEO Wizard and tried to add keywords to my pages. Was not working, so I deactivated them (along with Yoast and Google Analytics, which had been installed for a while but which I had never used) and then I found that all my page links were broken. I went into permalinks and changed the structure, saved it, and logged out, then logged back in and changed it back to the original structure and saved it, but the links were still broken. Any suggestion?