On the same line with the "New Posts" link, is a drop-down menu labeled "My Posts." Do those links work for you? The reason I ask is those links operate through the same external PHP script as "New Posts," which is search.php.
Is this something that just began happening? Have you been using this search successfully all along until suddenly now it no longer works?
Usually when a blank white screen is shown, it's because a requested file isn't present on the server. It's possible the server "hiccuped" at the same time you ran the search. Please let me know if it consistently gives you the blank white screen.