Features : export content types with FieldCollection
There are two solution to this problem, the first one is a bug in the module that can be fixed via this patch https://drupal.org/node/1084268

The second solution fixes a problem caused by orphan fields in field_collection_item table.
First try removing my_field via drupal interface, if it didn't exists try 
 searching your my_field in this table, if it existed , delete it


NOTE : the solution is dirty one, it worked for but it may have side effects, backup your database before trying it