For Some Reason

I Did use hacks a long time ago on mw2 ...i deleted the game since then and reinstalled it .. i dont inject no hack into the mp rip of alterIWnet and every time i still keep on gettin steam authurisation failed and its really Pi***** me of ? any ideaz of the problem ive tryed all of the things that people have posted and it still dosent help im just confused because as soon as i start the game for the first time i get the messege as soon as i enter a game ?

delete cache.xml and bootstrap folder
and run
iw4mp.exe
try it

If I remember correctly you wont find it more playable when you get rid of that error..