Strange color on transparent images on flat background, only in print.

Hi everyone, I have a print problem caused by the transparency of some objects.

All of them are .psd (some rbg some cmyk) and everything is fine on screen but when I print I get a different color that is exactly the "rectangular" of the object.
This is driving me mad.

See attachments:

I found 2 solutions:

1. Make one psd object as big as the document
2. Export pdf from Indesign, open in Ps at 1200dpi and save it again as pdf

As you can see these are NOT the solution of the problem but it's a temporary workaround.

Any ideas?

Thanks!