When I try to search by user to find posts by user, I get an error. I type in the name, and I get the autofill feature, so I know its the right name, and I know there are posts by the user. I have used this function before and it worked.
I click the search button with a down arrow next to it on the light blue bar across the top with home portal / user control panel etc. When I click on it there is an advanced search option that I click and it brings up a multi option screen. Searching by user on the right yields no results. Searching for kayak in all posts yielded no results either. I think the whole thing is toast.
Strange, I just followed your steps and did a search for myself in the right hand member name field (found 201 results) and then did a search for kayak on the left search option and got over 500 results.
You may want to try logging out and back in (although that should not really do anything but it will reset your cookies).
Can some other members try this out and see if the search is working for you?