It displays the first then, then quits. I'm not positive as to why
If you are using asynchronous with the same (global) request-object then, as I understand, only the first returned-response will be acted upon.
If synchronous then I still suggest creating a slight delay between requests will help with IE - but I may be wrong
. [The sleep() response is different as all the requests will stack-up, but return in quick succession after 1 second.]