Problem: The decision made by IDA was wrong and rolled back

 Description:
        This problem occurs when IDA had converted unexplored bytes to
        instruction(s) and later found that the decision was wrong.
        For example:

                mov     ax, bx
                db 0FFh, 0FFh

        0FFh, 0FFh can not be converted to an instruction, therefore
        the "mov" instruction can't be here.

        In this case IDA automatically destroys the instruction(s)
        and enlists the address as problematic.

 What to do:
        Examine the end result and modify it to the taste.