When I type something into the side bar search (widget) on my blog and wait for the ajax to kick in and do it's think, it always prints out:
No input file specified.
I'm using the k2 theme and I'm not certain that it's not a bug in the theme, but I'm guessing it's a regular WordPress bug. If it's k2's fault then let me know.
BTW, I'm also using the latest k2 theme release as of today.
See the error for yourself.
http://www.kyleabaker.com/ <-type something in side search and wait for the ajax to do the work for you (don't click search).