Perhaps you release the object too many times.
Open the debugger console by pressing Cmd + Shift + R. and then enter the following
break malloc_error_break
This will set a breakpoint at the beginning malloc_error_break, you can also try to print what the object is at 0xa68aca0
print-object 0x1068310
Another way to do this is to use NSZombieEnabled
Also worth reading this