Hi I have the same problem ACRO_BAL_ROLL/PITCH did you fond solution for this issue ?
I was tuning the PID parameters and just to start on fine tuning this message appears ! Arming is only possible if Prearm check is disabled !
Yes I just did that last night and worked. From firmware version AC 3.0.1 they change this parameters from 0 to 1 but also there is some problem with the voltage sensing after AC 3.0.1 see my discussion on page http://www.diydrones.com/forum/topics/ac3-1-rc5-spi-speed-problem?x...
I am also having the same problem after months 4 months of flying my drone. I did have my drone in a cradle trying to get the PID's right the night before but the next day I got the message. Have you found anything else out sense then?