1054 Unknown column 'c.parent_id' in 'on clause' - what did I break?!?

[kelvyn]

I wanted to use working store A as a basis for working store B, and as so much customisation and so many database additions has been done through plugins, I though the simplest thing would be to copy site a files and db, and then repoint siteb configures, empty the products and cats tables, and then easypopulate in the new data.

Except, I am getting:

1054 Unknown column 'c.parent_id' in 'on clause'
in:
[SELECT c.categories_id, c.parent_id, cd.categories_name as cName, cd2.categories_name as pName FROM categories c, categories_description cd LEFT JOIN categories_description cd2 ON c.parent_id=cd2.categories_id AND cd2.language_id='1' WHERE c.categories_id='10' AND cd.categories_id='10' AND cd.language_id='1' LIMIT 1]

And I have no idea why, or where this comes from! It should behave like the old store, just with no products!!!

[kelvyn]

After much experimentation, it appears to be related to Chemos Ultimate URLs, and there is a suggestion of a fix in this post
However, it didn't work for me, but I'll carry on posting on this subject in this thread now I know what it is.

[kelvyn]

...and a little while later, I FOUND THE ANSWER!

You need to go into the CONFIGURATION>SEO URLS and tick RESET SEO CACHE.

Yay! Also posted in the other thread, but left here too so the error is searchable.