OK, it sticks if I try to add an item in one of the tabs (will stick on that tab) even if I leave the page and come back. If I don't try to add an item and I leave the page it will go back to the first tab every time I come back.
I have an out of the box SharePoint Announcments list, Events list and Doc library list in the qDynmaicLayouts tab:
If I click the "Add new event" in the second image above a dialoge window pops up with the new event form:
When I hit Save here I am given the error I mentioned above. And now if I go to other pages and come back to this page it is stuck on the Events tab.