BTW the correct answer was provided to me by the cool guys on the C++ IRC channel. I leave it here just in case someone else needs the answer.
ss = & SoftwareSerial(0,1);
Here I'm pointing ss to a temporary. Trying to dereference it later is illegal and results in unexpected behaviour. It shouldn't even work.
So just use the "new" keyword to create a new instance and there you go
ss = new SoftwareSerial(0,1);