This looks like a great plugin, but I am having a problem with results that span multiple pages. I'm using WordPress 3.4.2 and version 1.0.2 of your plugin.
The number of blog posts is set to 10.
If I search for words that return less than 10 results, no problem.
If there are over 10 results but less than 20 then the first page is fine, but the Older Posts link returns a 404 error.
If there are over 20 results but less than 30 the first and second pages of results are fine, but the last page has the 404 error.
I have a test site setup at http://rubywhite.com/wp
You can try searching for 'john', 'mac', 'and'
This site uses the ThemeID responsive theme but I get the same results with the Twenty Eleven theme. I've tested with all other plugins deactivated with the same results.
Thanks for your help.