1) Create a User Group: userGroup
2) Create two pages: page1, page2
3) Assign the current user as a member of this userGroup.
4) Go to page2 and add the Blogs portlet for userGroup.
5) Go to page1 and add an Activities portlet for userGroup.
6) Go to user's page2 and add a Blogs entry.
7) Go to user's Welcome page and delete the default Blogs portlet.
8) Go to user's page2 and click on the link on the Activities portlet -> error:
The requested resource was not found.
It seems FindAction.getPlidAndPortletId() searches in the wrong group. In my case the groupId it searches in is 10199, however it should find the portlet in 11103, which is the groupId of the userGroup with 11102 userGroupId. If I run-time modify this value, it finds the Blogs portlet, but not the entry, so we have to modify that as well.
I couldn't test on trunk, as I was unable to add a new page.