I have actually been doing a lot of reading about netflow with cisco 3750X 48PF-S. my current version is 12.2(58)SE 1. I talked so cisco about this for 30mins. Netflow is not supported on the C3KX-NM-10G you would need the C3KX-NM-10G expansion module. This is the tricky thing though even though the netflow is not support the same config will work on version 12, but you will not get the desired results and sometime not get any results at all. you need to upgrade to ios version 15.0 1 SE and you will get the desired results that you are looking for.