python under java2

[motokoit]

For some reason i need to start a python script from inside a java code. The
main part of the code is something like this

try{
   Runtime rt = Runtime.getRuntime();
   System.out.println("start");
   Process proc =  Runtime.getRuntime().exec("python myscript.py");
   proc.waitFor();
   System.out.println("end");
} catch (Exception e){
   e.printStackTrace();
}

and so worked for months....but since some days ago the same instruction
does not work but execute without any exception, that is print either
"start" and "end"; the strangest thing happen when I call just

Process proc =  Runtime.getRuntime().exec("python myscript.py");

the execution looks like stalled and does not comes to an end printing just
the "start".

Some suggestion?
My machine is a Linux Mandrake64 10.1