Programmatically insert an image with caption
in the log entry it shows that [:db_insert_placeholder_7] and [:db_insert_placeholder_8] elements of the Array were empty - that might be the reason why Insert statement failed for the caption field: 

Array 
( 
[:db_insert_placeholder_0] =&gt; field_steps 
[:db_insert_placeholder_1] =&gt; node 
[:db_insert_placeholder_2] =&gt; 455 
[:db_insert_placeholder_3] =&gt; 863 
[:db_insert_placeholder_4] =&gt; article 
[:db_insert_placeholder_5] =&gt; 0 
[:db_insert_placeholder_6] =&gt; und 
[:db_insert_placeholder_7] =&gt; 
[:db_insert_placeholder_8] =&gt; 
[:db_insert_placeholder_9] =&gt; field_steps 
[:db_insert_placeholder_10] =&gt; node 
[:db_insert_placeholder_11] =&gt; 455 
[:db_insert_placeholder_12] =&gt; 863 
[:db_insert_placeholder_13] =&gt; article 
[:db_insert_placeholder_14] =&gt; 2 
[:db_insert_placeholder_15] =&gt; und 
[:db_insert_placeholder_16] =&gt; Wild Roses: fiori che sembrano appena sbocciati, che sottolineano ancora una volta la sua grande cifra stilistica, composizioni perfette per ogni dolce e speciale occasione. 
[:db_insert_placeholder_17] =&gt; full_html 
) 
in image_field_caption_field_attach_update() (line 234 of /sites/all/modules/image_field_caption/image_field_caption.module).


also, [:db_insert_placeholder_16] - contains a string with 173 characters - is the caption field big enough?

hope this helps