need help with selenium

[shiva upreti]

I wrote this code in python for submitting a login form: 

<code> 
from selenium import webdriver 
from selenium.webdriver.common.keys import Keys 
driver = webdriver.Firefox() 

driver.get('some url') 

elem = driver.find_element_by_name("username") 
elem.send_keys('13103666') 
elem = driver.find_element_by_name("password") 
elem.send_keys('as') 
driver.find_element_by_name("btnSubmit").click() 
#nothing happens from here 
print driver.page_source 
print "test" 
</code> 

After clicking on submit button, a message is displayed on the same page whether login was successful or not. 
However after clicking on submit button, I lose control over the web page. I can't use any selenium functions now like 'driver.find_element_by_name()'. 

Initially everything works fine. I can enter username and password using selenium as written in my code, but once I click on submit button or press return key(tried both using selenium), any script written after that(involving web driver) doesnt seem to work. Even driver.close() doesnt work. 
This is the form I am trying to submit: 
<form name="frmHTTPClientLogin" target="_parent" method="post" onsubmit="return checkSubmit();" action="httpclient.html"> 

The submission is successful, however after submission I cant verify if login was successful or not because of the issue I posted above. 
Do I need to switch web handle? If, then how. 

Any help will be highly appreciated.