20D Error 01

[coolay_11]

am facing a problem with my EF 100-300 IS, it's clean lense but i did drop it from 20cm hight into my bed.. after that am reading Error 01 if i load it with my 20D, when i use my other lensses the 20D body works normaly.
i did clean the clean & alost new attaching points (lens & camera body) but still facing the problem.
i need your helpfull suggestion to find out what is the problem about
thx everyone