Problem with real/imag/conjugate

I get the wrong answer for real/imag for some forms of complex numbers.
For example:

a := (-1*%i)^(1/2) 

b := (%i)^(3/2)

are both equivalent, but imag/real gives complex (and incorrect) answers
for "a" (ie, real(a) and imag(a) are both complex), but I get the right
answers for "b". Also "conjugate" fails on both with an error message.

Am I missing something here? 

I am using Axiom compiled from the latest "Gold" source. 

Thanks,
Arnold