If the vCloud Web UI works and you have your public addresses filled in correctly, you'll want to post here:
http://communities.vmware.com/community/vmtn/developer/forums/vcloudapi
This particular forum is for vCloud Director as a whole, excluding the API component.
So if you can test with the vCloud Director website, and it fails as well ... I'd probably want to see log files from vCloud Director containing the time frame.