Weird error updating table - Mailing list pgsql-general

Today we received a very odd error from our PostgreSQL database:

"update category_product set product_is_active = p.is_active, product_status_code = p.status_code from product p where category_product.product_id = p.product_id  and category_id = 1001415;">:

    Next exception:SQL State:XX000 -- error code: 0 -- msg: ERROR: could not read from hash-join temporary file: Unknown error: 0

Any one know what that could mean? I've only seen it once so far. Hopefully it's not a sign of some sort of impending database doom.

Thanks,