You should look at server logs to see error details. Whenever the process shows a blank canvas there has been parsing issue which are reported in the logs.
I believe your particular issue is with Lanes. The jBPM Eclipse editor with which the examples were created with does not support Lanes visually so it does not generate the BPMNDI info for them, but the Designer has visual support and is saying that it cannot find that positioning info.
In the evaluation process BPMN2 you are uploading, remove the laneset definitions, then upload again. In Guvnor then place the lanes back. Sorry but the Eclipse editor in this regard is not generating valid BPMN2.
Hope this helps.