Have you entered the right mode (I think on the ti-83 it was: 'a+bi', in stead of 'real')?
Can you give this complex number.
Did you use for the - sign in the exponent the: operation - (from the difference), or the sign - (to indicate a negative number)? Because that's often a problem. Now, you have to take the 'sign' -.
Do you have to take the square root or just divide the two complex numbers?
Most calculators only have very limited support for complex numbers. For instance the graphical one on my desk right now cannot even perform exponentiation of complex numbers at all, and hence cannot calculate the square root of a complex number.
Also, did you put brackets when evaluating 4.5239x10^-6i? If you didn't it's quite possible the calculator understood 4.5239x10^(-6i), not 4.5239x10^(-6) i, and your calculator most likely cannot evaluate complex exponentiation hence math error.
you still haven't stated what calculator you are using.
my TI-84 does this operation fine in classic mode ... will not do it using the "pretty print" mode.
the entire output (not shown in the screen shot) is