error with Firefox Binary 'The browser appears to have exited' - python-2.7

Question

I have problem with selenium and Firefox when i run my code below:
from selenium import webdriver
from selenium.common.exceptions import TimeoutException
from selenium.webdriver.support.ui import WebDriverWait
from selenium.webdriver.support import expected_conditions as EC
from bs4 import BeautifulSoup
import urllib2,cookielib
import re
from pyvirtualdisplay import Display
import urllib
import urllib2
import httplib2
from os import system
display = Display(visible=0, size=(800, 600))
display.start()
name = 'test'
driver = webdriver.Firefox()
driver.get("http://example.com")
driver.switch_to_default_content()
inputElement = driver.find_element_by_name("name")
inputElement.send_keys(name)
inputElement.submit()
print "Please wait for 5s to get results.."
content = driver.page_source.encode("utf-8")
html = str(content)
soup = BeautifulSoup(html)
print soup
display.stop()
driver.close()
And i get this error:
Exception in thread command9:
Traceback (most recent call last):
File "/usr/local/lib/python2.7/threading.py", line 551, in __bootstrap_inner
self.run()
File "/usr/local/lib/python2.7/threading.py", line 504, in run
self.__target(*self.__args, **self.__kwargs)
File "plugins/help_plugin.py", line 165, in handler_search
search_number_ar(type, source, parameters)
File "plugins/test.py", line 230, in search_test
driver = webdriver.Firefox()
File "/usr/local/lib/python2.7/site-packages/selenium-2.45.0-py2.7.egg/selenium/webdriver/firefox/webdriver.py", line 59, in __init__
self.binary, timeout),
File "/usr/local/lib/python2.7/site-packages/selenium-2.45.0-py2.7.egg/selenium/webdriver/firefox/extension_connection.py", line 47, in __init__
self.binary.launch_browser(self.profile)
File "/usr/local/lib/python2.7/site-packages/selenium-2.45.0-py2.7.egg/selenium/webdriver/firefox/firefox_binary.py", line 66, in launch_browser
self._wait_until_connectable()
File "/usr/local/lib/python2.7/site-packages/selenium-2.45.0-py2.7.egg/selenium/webdriver/firefox/firefox_binary.py", line 100, in _wait_until_connectable
raise WebDriverException("The browser appears to have exited "
WebDriverException: Message: The browser appears to have exited before we could connect. If you specified a log_file in the FirefoxBinary constructor, check it for details.
my code running in vps and i use selenium-2.45.0 and firefox.x86_64-31.6.0.
I try alot of ways to solve my problem but nothing working with me.
I try to update selenium and i try to downgrade firefox and alot of solution.
Just to know when i run my code for the first time it work but when i run it again it show me the above error.
I hope someone help.