[Typo3] Upgrade to 3.8.1 TemplaVoila Error

[Sandy Matheson]

I have just upgraded one of our sites from 3.8.0 to 3.8.1 and I am now
getting the following error when I try to access any page:

TemplaVoila ERROR:
Couldn't find a Data Structure set for table/row "pages:2".
Please select a Data Structure and Template Object first.

The same error also appears in the backend when I access the Page
Module.

I have also noticed that the root page of the website points to a
SysFolder calle dTemplates - but this is now entirely empty. This is
where the TemplaVoila templates should be!

Is there a way fo recovering the templates or do I need to rebuild
them from scratch?

Why would an upgrade do this?

Any help much appreciated.

Sandy Matheson