When you call an ITX map from an integrated product (ACE, B2Bi, ITX-A, etc) then you are overriding the input card to STREAM. The original adapter would have been Excel, and therefore it will fail.
Output via Design Studio:
1|This is some data
...and the same map called via a Java API call:
PK ! bî�h^ � [Content_Types].xml......
I will demonstrate a potential workaround for this.