Totally confused about phasing

Something very strange, and I guess very wonderful, just happened to my system. I got Stereophile Test CD 3 this morning, and played the second track, stereo phasing. To my surprise, it appeared that my speakers were out of phase. I looked at the back of my speakers and amp, and everything was connected corectly. I followed the advice in the CD booklet, and switched the connections on the back of ONE speaker. So now, red is going to black, and black is going to red. The change in sound almost gave me a heart attack. The imaging is now perfect!!! Before it was awful.

So am I to understand that something was marked wrong, either on my speaker cable or on the back of the speakers, or on the amp? I don't get it!!! I'm using Analysis Plus Oval 9 speaker cable, Silverline SR-15 speakers, and an Electrocompaniet ECI-3 amp.