OpenCV does not detect faces on Eclipse/Win7

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Hi all, I'm pulling my hair around this one. I have followed tutorials, unzipped opencv, added my library in eclipse, copy/pasted the simple face detection program, and now it runs fine but... it doesn't detect any face, even with faces that are easy to detect and with images that people have successfully used with the same sample code. The catch is that the program runs fine (no error) but does not detect any face, whatever the image I give it (I've tried on larger banks of frontal face images, no luck: 0 face detected). I've even tried the cat face detection with some very obvious images, and still nothing is detected. Eye detection returns 0 eye detected as well.

To make sure it is really using the x64 DLL, I've also tried changing the DLL directory to x86 and I do get an error saying that it cannot open a 32 bit DLL on a 64 bit system, which confirms it is indeed loading the DLL. I've tried this with the latest 2.4.13 version of opencv as well as the previous version 2.4.12, with no luck. Anyone ever faced this kind of issue? Any clue what could be causing this?

I am on Windows 7 SP 1, x64 obviously. Eclipse is a little old: Mars.1 release (Build id: 20150924-1200). UPDATE: I have installed the latest Eclipse (Neon.1a Release (4.6.1)) and get the exact same results. JDK is 1.8.0_60.

Thanks!

JY.