Illegal instruction? working code for months?

[korenron]

this is very strange......

I have created a file with all the import:

import time
from datetime import datetime
import Adafruit_SSD1306
import subprocess
from PIL import Image
from PIL import ImageDraw
from PIL import ImageFont

import os
import sys
import random
from random import randint

import RPi.GPIO as GPIO 

run it , didn't get any error

then I try to run my working full code
and it works ....

how could it be ?
I didn't change anything \ didn't reboot the pi since yesterday \ didn't run update&&upgrade