I got this error when I did Catalog > Manage Categories
And this error when I did Catalog > Manage Products > Add Products > Continue
I already contacted my hosting, and they said that my problems are not connected directly to their services, server software and/or modules installed on the server..
They gave me these recommended links to me, but I don't understand any of them,
I really hope that someone in Magento Forums could help me, because I cannot add any products into my website.
Thanks in advanced.