After the SetExpressCheckout

I do get the following return:

[TIMESTAMP] => 2011-12-30T12:10:47Z
[CORRELATIONID] => a481fba2e19e4
[ACK] => Failure
[VERSION] => 65.1
[BUILD] => 2271164
[L_ERRORCODE0] => 10003
[L_SHORTMESSAGE0] => Missing argument
[L_LONGMESSAGE0] => Item name, amount and quantity are required if item category is provided.
[L_SEVERITYCODE0] => Error

I do understand that the return states that one of my arguments are missing, but this is what is send to paypal:

[VERSION] => 65.1
[METHOD] => SetExpressCheckout
[RETURNURL] => http://mysite.com/paypal...b9b0499051776d135866...
[CANCELURL] => http://mysite.com/paypal/ECCancel.php
[L_PAYMENTREQUEST_0_NAME0] => Regular
[L_PAYMENTREQUEST_0_DESC0] => Regular fee
[L_PAYMENTREQUEST_0_AMT0] => 150.00
[L_PAYMENTREQUEST_0_QTY0] => 1
[L_PAYMENTREQUEST_0_ITEMCATEGORY0] => Digital
[L_PAYMENTREQUEST_0_NAME1] => Vegetarian option
[L_PAYMENTREQUEST_0_DESC1] => Use the vegitarian option
[L_PAYMENTREQUEST_0_AMT1] => 0.00
[L_PAYMENTREQUEST_0_QTY1] => 1
[L_PAYMENTREQUEST_0_ITEMCATEGORY1] => Digital
[L_PAYMENTREQUEST_0_NAME2] => Diet
[L_PAYMENTREQUEST_0_DESC2] => Select this when you have specific diet options, provide information in the comment box
[L_PAYMENTREQUEST_0_AMT2] => 0.00
[L_PAYMENTREQUEST_0_QTY2] => 1
[L_PAYMENTREQUEST_0_ITEMCATEGORY2] => Digital
[L_PAYMENTREQUEST_0_NAME3] => Conference Dinner
[L_PAYMENTREQUEST_0_DESC3] => Attend the conference dinner at friday evening
[L_PAYMENTREQUEST_0_AMT3] => 35.00
[L_PAYMENTREQUEST_0_QTY3] => 1
[L_PAYMENTREQUEST_0_ITEMCATEGORY3] => Digital
[L_PAYMENTREQUEST_0_NAME4] => Admnistration Costs
[L_PAYMENTREQUEST_0_DESC4] =>
[L_PAYMENTREQUEST_0_AMT4] => 10.00
[L_PAYMENTREQUEST_0_QTY4] => 1
[L_PAYMENTREQUEST_0_ITEMCATEGORY4] => Digital
[PAYMENTREQUEST_0_AMT] => 195.00
[PAYMENTREQUEST_0_CURRENCYCODE] => EUR
[PAYMENTREQUEST_0_ITEMAMT] => 195.00
[REQCONFIRMSHIPPING] => 0
[NOSHIPPING] => 1



What am I doing worng? Can you help me out?

-- Martijn