I realise this is an old thread but just spotted it... and I have had a lot of problems to overcome in recent years with this exact issue. If its any help (probably not...) mitsi PLCs can be phenomenally difficult to pull ladder back out of them if you don't have the original source code. Generally with the Q series, Mitsubishi GX Developer, or GX IEC Developer will have been used to program them. The problem is that both of these tend to crunch your ladder down into a form of machine code before downloading it into the PLC in the first place, which when sucked back out is (almost) completely unrecognisable to the average human. If your still struggling with it let me know and I can potentially offer some advice - but, I would say in the first instance, make every and all efforts to find who the last person or company who worked on that PLC, and get the source code off them - because this will be ladder/function block/recognisable.