Hi TillyT
I had the same problem with my products and orders, it occurred over nite and appeared yesterday morning when I went to fill my orders.
I could not find any fix for it, so I restored the site with a backup from the day before the errors occurred. That fixed the problems. But I had to re enter all the orders from new order emails that came in after the backup. Still do not know what caused it. But its fixed.
Tom