I do not see the EPC itself being the issue here. It seems we have found an exception when we try and create the PowerDesigner file from Visio - have you tried other EPC diagrams from Visio? Is this issue limited to just one EPC diagram or several? It could also be an issue with the stencil used, we use the stencil to try and define what drawing elements should become what metaclass in PowerDesigner.
If possible, you can share the EPC with me and I can try and reproduce the issue.