When you are reading the XML file into your local Clbfile parameter, what are the values for the Adxirs and Adxium parameters? I_FILE is expecting the contents of the file in a Clbfile variable, something like the code below will perform a full read of the XML file and then you can then pass it to AOWSIMPORT.  Alternatively make use of AOWSEXPORT to export an example record and then see the content formatting within the variable O_FILE looks like. 

Local Char XLINE(250)
Local Clbfile I_FILE(3)

Openi filpath('tmp','XML','txt') Using [FIC1]
Iomode Adxirs '' Using [FIC1]
Iomode Adxifs chr$(13)+chr$(10) Using [FIC1]
Iomode Adxium 50 Using [FIC1]
while fstat = [v]CST_AOK
Rdseq [L]XLINE Using [FIC1]
Append I_FILE, [L]XLINE
Wend
Openi Using [FIC1]

Thanks Regard Hulsbos  I had been exporting the XML already to create the XML file and then attempting to re-import it.  I found the problem - it was the quote's in the XML.  The output is XML, so contains quotes in the XML header.  I need to encode these quotes before doing the import - and that all works now.  So, be careful with your encoding is the answer....