I am having the same problems. Getting a 500 Error when it finds the results:
<html><head>
<meta http-equiv="content-type" content="text/html;charset=utf-8">
<title>500 Server Error</title>
</head>
<body text=#000000 bgcolor=#ffffff>
<h1>Error: Server Error</h1>
<h2>The server encountered an error and could not complete your request.<p>If th
e problem persists, please <A HREF="
http://code.google.com/appengine/community.html">report</A> your problem and mention this error message and the query that c
aused it.</h2>
<h2></h2>
</body></html>
[5.32 Mkey/s][total 305056972800][Prob 0.0%][50% in 77.7d][Found 1] S