The reason you have frost is due to the vapor barrier(Tar paper) being on the wrong side of the heated space.It is trapping the water and freezing it.
The tar paper is also vapor permeable, which means it cannot hold back the water from the block. If you had used plastic instead of the tar paper and sealed it at all the joints, this may have worked to delay water migration and let the water disperse into the room. If you where to install the plastic, you may have trapped the water behind the plastic and caused serious water issues to the wall system.
To sum it up,
Vapor barriers always should face the heated side of the space,and be permeable. Tar paper or kraft faced is best.
Plastic or waterproof membranes can be placed on the interior, only after the exterior is up to par. Remember there is really no waterproof, only water control and diversions.
Try Building Science Corporation
for more info for your issues.
Hope this helped.