You probably have two distinct installation of the logilab
package, one for logilab-common and the other for logilab-astng. Take a look at:
import logilab
print logilab.__path__
You should fix things (adjust PYTHONPATH?) so that you get the directory containing the common
subdirectory there.
Also notice that for recent version of pylint (>= 1.0), logilab-astng has been replaced by astroid
.