I also concur with Aristotelis, Martin and Carol: the probelm only appeared after updating acroread (I am using a 64 bit Ubuntu 12.04.1), that, in fact, was done moments ago. The nagging file is small (NPP...), but unles you discard it, the file grows multiples
of 72 bits EVERYTIME you open Firefox.
I also concur with Aristotelis, Martin and Carol: the probelm only appeared after updating acroread (I am using a 64 bit Ubuntu 12.04.1), that, in fact, was done moments ago. The nagging file is small (NPP...), but unles you discard it, the file grows multiples
of 72 bits EVERYTIME you open Firefox.