The most common reason for this is a broken tab on a tabbed island.

1. Figure out which page has the bad tab island.

2. As you can see in my example below. I have two tabs, "tests tab", and "pte"

- In the SQL table PWPageIslands you will see the two tabs in the Pref String column.

     test tab|cf78ca76-e648-4e3f-b9f2-37c185a543aa~

     pte|e76363a9-3d4c-462f-b646-54bc288e3cad~

- Notice how there is a | between the tab name and the GUID. That GUID needs to be 32 digits long. If you see one the is not 32 digits long you need to remove it.

- For example, if there is

test tab|cf78ca76-e648-4e3f-b9f2-37c185a543aa~
pte|e76363a9-3d4c-462f-b646-54bc288e3cad~test tab2|e23465f3-~

- You would have to remove "test tab2|e23465f3-~" because the GUID isn't 32 digits long.