The eCart name columns seems to get its value from the Last name column in your form.
if you do not enter a last name in the form, then the item does not have a name. When the item information is sent to paypal, the Item must have a name. If not, you get the error you specify.
When I go thorough your page, if I enter 1 as the amount and test as the last name, it foes to paypal correctly.
If I do not enter a last name, I get the error.