I have downloaded ec2rc.sh file on my computer and sourced it. When I try to use ec2 commands such as:

ec2-describe-images

I get an error:

Unexpected error:
org.codehaus.xfire.fault.XFireFault: Server returned error code = 400 for URI : http://mycloud.org:8773/services/Cloud. Check server logs for details
    at org.codehaus.xfire.fault.XFireFault.createFault(XFireFault.java:89)
    at org.codehaus.xfire.client.Invocation.invoke(Invocation.java:83)
    at org.codehaus.xfire.client.Invocation.invoke(Invocation.java:114)
    at org.codehaus.xfire.client.Client.invoke(Client.java:336)
    at org.codehaus.xfire.client.XFireProxy.handleRequest(XFireProxy.java:77)
    at org.codehaus.xfire.client.XFireProxy.invoke(XFireProxy.java:57)
    at com.sun.proxy.$Proxy12.describeImages(Unknown Source)
    at com.amazon.aes.webservices.client.Jec2Impl.describeImages(Jec2Impl.java:534)
    at com.amazon.aes.webservices.client.cmd.DescribeImages.invokeOnline(DescribeImages.java:158)
    at com.amazon.aes.webservices.client.cmd.BaseCmd.invoke(BaseCmd.java:1061)
    at com.amazon.aes.webservices.client.cmd.DescribeImages.main(DescribeImages.java:182)
Caused by: org.codehaus.xfire.XFireRuntimeException: Server returned error code = 400 for URI : http://mycloud.org:8773/services/Cloud. Check server logs for details
    at org.codehaus.xfire.transport.http.HttpChannel.sendViaClient(HttpChannel.java:130)
    at org.codehaus.xfire.transport.http.HttpChannel.send(HttpChannel.java:48)
    at org.codehaus.xfire.handler.OutMessageSender.invoke(OutMessageSender.java:26)
    at org.codehaus.xfire.handler.HandlerPipeline.invoke(HandlerPipeline.java:131)
    at org.codehaus.xfire.client.Invocation.invoke(Invocation.java:79)
    ... 9 more

On the controller node, there is nothing to report in keystone.log. I get the following message in nova.log

2013-09-18 13:20:45.389 4958 INFO nova.ec2.wsgi.server [-] (4958) accepted ('130.237.221.115', 65154)

2013-09-18 13:20:45.400 4958 ERROR nova.api.ec2 [-] Unauthorized: Signature not provided
2013-09-18 13:20:45.401 4958 INFO nova.api.ec2 [-] 0.1073s myhost POST /services/Cloud None:None 400 [ec2-api-tools 1.6.10.0] text/xml text/xml
2013-09-18 13:20:45.402 4958 INFO nova.ec2.wsgi.server [-] myhost "POST /services/Cloud HTTP/1.1" status: 400 len: 314 time: 0.0022440