Right I have checked the errorlog and found some interesting debug information. Here are the bits that look the most interesting.

<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:xsi="http://www.w3.org/1999/XMLSchema-instanc
+e" xmlns:SOAP-ENC="http://schemas.xmlsoap.org/soap/encoding/" xmlns:S
+OAP-ENV="http://schemas.xmlsoap.org/soap/envelope/" xmlns:xsd="http:/
+/www.w3.org/1999/XMLSchema" SOAP-ENV:encodingStyle="http://schemas.xm
+lsoap.org/soap/encoding/">
  <SOAP-ENV:Header>
    <impl:email xmlns:impl="https://adwords.google.com/api/adwords/v2"
+>me@ourcompany.com</impl:email>
    <impl:password xmlns:impl="https://adwords.google.com/api/adwords/
+v2">mypassword</impl:password>
    <impl:useragent xmlns:impl="https://adwords.google.com/api/adwords
+/v2">Existem -- Report Service Demo</impl:useragent>
    <impl:token xmlns:impl="https://adwords.google.com/api/adwords/v2"
+>mLJY5JKVDelqtK74RxOt5w</impl:token></SOAP-ENV:Header>
  <SOAP-ENV:Body>
    <scheduleReportJob xmlns="">
      <customReportJob xmlns:impl="https://adwords.google.com/api/adwo
+rds/v2" xsi:type="impl:CustomReportJob">
        <aggregationType>Summary</aggregationType>
        <endDate>2005-08-11T23:59:59</endDate>
        <campaigns>5214135</campaigns>
        <name>test</name>
        <customOptions SOAP-ENC:arrayType="xsd:ur-type[5]">
         <item>AveragePosition</item>
          <item>Clicks</item>
          <item>Cpc</item>
          <item>Keyword</item>
          <item>AdGroupId</item></customOptions>
        <startDate>2005-08-11T00:00:00</startDate>
      </customReportJob>
    </scheduleReportJob>
  </SOAP-ENV:Body>
</SOAP-ENV:Envelope>
SOAP::Transport::HTTP::Client::send_receive: HTTP/1.1 500 Internal Ser
+ver Error
[download]

Do you think it's this bit which is causing the problem?

SOAP-ENC:arrayType="xsd:ur-type[5]"
[download]

Here is the error response I am getting.

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envel
+ope/" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://
+www.w3.org/2001/XMLSchema-instance"><soapenv:Body><soapenv:Fault><fau
+ltcode>soapenv:Server.userException</faultcode><faultstring>org.xml.s
+ax.SAXException: No deserializer defined for array type {http://www.w
+3.org/1999/XMLSchema}ur-type</faultstring><detail><ns1:stackTrace xml
+ns:ns1="http://xml.apache.org/axis/">org.xml.sax.SAXException: No des
+erializer defined for array type {http://www.w3.org/1999/XMLSchema}ur
+-type
        at org.apache.axis.encoding.ser.ArrayDeserializer.onStartEleme
+nt(ArrayDeserializer.java:267)
        at org.apache.axis.encoding.DeserializerImpl.startElement(Dese
+rializerImpl.java:399)
        at org.apache.axis.encoding.DeserializationContext.startElemen
+t(DeserializationContext.java:1038)
        at org.apache.axis.message.SAX2EventRecorder.replay(SAX2EventR
+ecorder.java:159)
        at org.apache.axis.message.MessageElement.publishToHandler(Mes
+sageElement.java:1138)
        at org.apache.axis.message.RPCElement.deserialize(RPCElement.j
+ava:199)
        at org.apache.axis.message.RPCElement.getParams(RPCElement.jav
+a:342)
        at org.apache.axis.providers.java.RPCProvider.processMessage(R
+PCProvider.java:146)
        at org.apache.axis.providers.java.JavaProvider.invoke(JavaProv
+ider.java:319)
        at org.apache.axis.strategies.InvocationStrategy.visit(Invocat
+ionStrategy.java:32)
        at org.apache.axis.SimpleChain.doVisiting(SimpleChain.java:118
+)
        at org.apache.axis.SimpleChain.invoke(SimpleChain.java:83)
        at org.apache.axis.handlers.soap.SOAPService.invoke(SOAPServic
+e.java:450)
        at org.apache.axis.server.AxisServer.invoke(AxisServer.java:28
+5)
        at org.apache.axis.transport.http.AxisServlet.doPost(AxisServl
+et.java:637)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:709
+)
        at org.apache.axis.transport.http.AxisServletBase.service(Axis
+ServletBase.java:301)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:802
+)
        at com.google.gse.HttpConnection.runServlet(HttpConnection.jav
+a:393)
        at com.google.gse.HttpConnection.run(HttpConnection.java:334)
        at com.google.gse.DispatchQueue$WorkerThread.run(DispatchQueue
+.java:219)
</ns1:stackTrace></detail></soapenv:Fault></soapenv:Body></soapenv:Env
+elope>
[download]

There is more about the error response if that's any help.