twitter app wont let me log in

everytime i installed a twitter app for my ipod touch
either twitter , echofon , twitterific , twittelator
all the apps for twitter would not work
it keeps saying i have the wrong login and password combination
which is untrue because when i logged into twitter from the mobile site on my safari , it worked
and i even changed my password a couple of times to see if that was the problem
but it still didnt work
HELP PLEASE !