  For a class of pointed Hopf algebras including the quantized enveloping
algebras, we discuss cleft extensions, cocycle deformations and the second
cohomology. We present such a non-standard method of computing the abelian
second cohomology that derives information from the non-abelian second
cohomology classifying cleft extensions. As a sample computation, a quantum
analogue of Whitehead's second lemma for Lie-algebra cohomology is proved.
