Did you try any of the drives in another laptop or PC?
It is not impossible that the laptop could be to blame, just improbable given that it was fine for eleven months after the first replacement. I think that you may have just been unlucky (generally if a new component is going to fail, it does so in the first month). However to answer your question, the IDC cable could be faulty or the IDE controller or the power lead or the supply to the power lead. The action of disconnecting the drive may be clearing the fault.
I would be tempted to cut my losses and buy a new laptop, there are so many bargains to be had now on what will almost certainly be a a much higher spec machine.