Photoshop :: Bad PDF Transparency Rasterizing

i'm having trouble rasterizing an .ai file.The source of this file is a pdf file that was probably not meant for print. I extracted only the fragment that's needed to describe the problem.As you can see, the transparency doesn't rasterize well (right image).I rasterized this CMYK .ai in photoshop CS5 with CMYK mode so it would preserve overprint (although RGB rasterizing renders badly too).
 
such files have, for what i know, always rendered correctly in the past.There are no spotcolors in the file.My problem is not getting this specific file rendered correctly (i can think of some workarrounds, like first flattening in Illustrator). My problem is finding and fixing the cause, as our scripted workflow heavily depends on this pdf to photoshop rasterizing feature. URL....