Running for weeks, now a problem

[chalfontgifts]

My whats new sidebox has suddenly started bringing this up.

1104 The SELECT would examine more than MAX_JOIN_SIZE rows; check your WHERE and use SET SQL_BIG_SELECTS=1 or SET SQL_MAX_JOIN_SIZE=# if the SELECT is okay
in:
[select p.products_id, p.products_image, p.products_tax_class_id, p.products_price, pd.products_name, p.master_categories_id from (products p left join products_description pd on p.products_id = pd.products_id ) where p.products_id = pd.products_id and p.products_status = 1 ]

Also if you go to my new products in the categories sidebox, it brings up a http 500 internal server error.
This also has been working before.

I have had to disable the whats new sidebox.

Url is www.chalfont gifts.co.uk (link broken to stop google crawl)

Any idea what this means, and how I can fix it.

Regards
Laurie