AifGatewayReceiveService unable to read xml file

I try Importing customers into Dynamics AX 2012 using AIF.

this is the error message I get (if you click on the image, then it will appear larger!):

I followed Ashoks walk trough (http://erptechnician.net/2011/11/07/importing-customers-into-dynamics-ax-2012-using-aif/#more-6) to create a basic example for AIF.

I do not expect an answer to solve my question but I need a few hints. I do not konw where to start looking for my problem.

thx!

I suck at AIF, but normally when a file does not behave in import/export/whatever, I start by checking the permissions of the file and folders are sufficient.