suddenly a button does not respond anymore in IE - but still does in Firefox !

Why suddenly a button (on my login-page) does not respond anymore onIE, but still does in Firefox. I did not make any changes to the codeof that page!
Thank you for any information concering this problem!
Regards,
Fabian
Please read the following FAQ:
Buttons do not submit anymore in IE
thank you very very much!
1) What I did is to place the "aspnet_client" folder and it's content in my webapplication-folder,
2) I changed in the WebUIValidation.js - file the following
function ValidatorCommonOnSubmit()
{
event.returnValue = !Page_BlockSubmit;
ret_Val = !Page_BlockSubmit;
Page_BlockSubmit = false;
return ret_Val;
}
3) I entered into the web.config the following :
<system.web>
<webControls clientScriptsLocation="aspnet_client/system_web/1_1_4322/"/>
</system.web>
And now it works !
Thank you again !
Regards,
Fabian