We'd need some screen shots of the page and the seps preview to confirm, but I suspect you are using the RGB transparency blend space and converting your 100K to a 4-color mix.
Where do you print? Laser? It should not appear on offset.
You should use psd, not png.
The file was a RGB, which I converted to CMYK. What do I need to do? I can't have a darker Black behind my transparent images. Thqnk you.
When you place images in InDesign you should them in RGB, even if you export CMYK files. You need only to correct the transparency blend space!
But you did not answer my import question: Do you see it on the laser or on offset?
I think you encounter this phenomen: http://indesignsecrets.com/eliminating-ydb-yucky-discolored-box-syndrome.php