I have seen this error before, when I have seen this error in the past with others it was due to a bad value within the item. A common culprit is the size of the item's name, it can only be 31 characters in length. There are many more specific limitations that in place for the line items, they are listed here in the developer guide for Authorize.NET AIM:
The line item requirements start on page 20 in this pdf doc. Take a look at these and check your items to ensure that they meet the requirements.