I also get that error... If I don't enter either a word or a member's name in the appropriate search box. Which makes sense. Kind of difficult to get a proper return on a search without giving it something to search for.
On the other hand, if you've entered a field appropriately and still not getting a result, that'd be a problem.
It's not the clearest, since the tab is one uniform colour, but the "Search.." text is where you'll enter your query. I got caught out on that too this morning, when I would type the keywords into the username field (and then wondered why that was the top field).
Just searched "GTPlanet" with your name @BobK , and got the usual results.
