I couldn't tell you really. One of the first trees I ever did long ago was an Alberta Spruce and the same thing happened to me. If you still have green, it isn't dead yet, but to the cause, couldn't tell you. I have never attempted another Spruce, but from what I have heard the Alberta Spruce are difficult to work with. I have heard they get a fungus very easily that results in white stuff on the trunk. I have also heard they are impossible to shape also. From what I understand, it take years for them to conform to wiring because they are so "rubbery" and will spring right back to their original form. Basically, i have heard the speices was a nightmare to work with so I never tried it again. Best of luck and check the link below to see if you can spot the problem. Also, you may want to post a little more info or a pic to get better advice. For instance, did you repot the tree? Bareroot it? How much foliage did you cut off, etc....?
http://www.bonsai-bci.com/species/spruce.html