Thanks for that reply. I tried to recreate this problem using the exact same versions of both Jira and the Portfolio plugin. But so far I have not been able to recreate this error. I also have not found any other reports of this problem just yet. So I'm not sure this is a bug just yet. I suspect that this is a problem specific to your environment right now.
What happens if you try to view the other portfolio links in the left navigation menu on that page? Such as 'Portfolio License details'? Does this show that the product has a license activated for it yet? Or do you see a similar error box.
I suspect that the Portfolio plugin has not fully been initialized in the JVM that Jira is using. In turn it seems that the functionality of this plugin is not working as a result. I would be interested to see if you can also take a closer look into the $JIRAHOME/log/atlassian-jira.log file for additional information here. I would be interested to see what warnings/errors might exist in this log file at the time the portfolio plugin is loaded up, as well as when trying to view these pages. The error messages there should be able to tell us much more about the nature of this problem and how we can further address it.