Sounds to me like a couple wires in that Sub Panel are crossed (that is hooked up wrong)
NOTE: Caution, you will be working with HOT wiring, SHOCK hazard, Take precautions or get someone who knows what the blazes he's doing (IE: ME) to do these tests... I also have the hardware.
how to test, You need a 120 volt test light or multi-meter. I like test lights cause they are "Quick and dirty"
Turn off ALL breakers in the box.. One probe to the white wire bus You can even screw it down if you like (makes it easier to do this test)
now probe the black wires
IF any wire connected to a breaker is "hot" that is your problem NO breaker wires shoudl be HOT
There is also supposed to be a black wire hooked to a bus bar.. The bar the breakers connect with (A black wire not connected to a breaker) This one SHOULD be HOT. if it' snot, your box is mis-wired.
If you are in S.E. Ga.. So am I.