I had this same issue when google geocoding and parsing the XML result. Seems that when run via an SQL job the XML result was being truncated.
Found the solution here: http://www.progtown.com/topic376715-a-problem-with-spoagetproperty-p2.html
Had to put:
SET TEXTSIZE 2147483647;
at the start of my stored proc.
The decision: in the procedure beginning to write the instruction
SET TEXTSIZE 2147483647
Or any other size, sufficient what to find room returned http the server for the answer.
The reason of such behavior of the server, I think, it is clear.
The moderator: and for zoom-in – the warning