I used to bind event to my button like :
$(\"input[name=add]\").live(\"click\",function(){...});
But I got another function to make them \"
You'll want to use the prop function instead of attr:
$(this).prop("disabled", true);
and
$(this).prop("disabled", false);
EDIT
OP was using jQuery pre 1.6.1, which was why attr for disabled wasn't working quite right (for older IE). While prop is preferred for disabled, post 1.6.1 attr should (and does) work as well.