I have been using this widget for several months on one of my sites, and was in the middle of installing it on a second (uploaded and activated it, just never actually put the widget in the sidebar). In the past it has worked reasonably well for me. However, it appears the recent upgrade to 1.0 (which I believe addresses the search result URL issue) is causing some problems.
All my page links, category links, and tag links are redirecting to the most recent post. This is regardless of whether the widget has actually been placed in the sidebar, or not. As long as it has been activated I have this problem.
I have deactivated it in one site, and uploaded an older version to the other (because the widget is a vital part of that site's navigation). Both are working fine, now.