python under java

[motokoit]

For some reason i need to start a python script from inside a java code. The
technique is standard

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

and so worked for months....

since yestarday the same instruction does not work but the line is correct
because from the terminal prompt it works! By the way the instruction work
for every other command, for example

Process proc =  Runtime.getRuntime().exec("emacs")

works. Some suggestion?
My machine is a Linux Mandrake64 10.1