This is a frequent asked question which can be solved simply with a line of code with javascript.
The problem
If you use Internet Explorer you can find an annoying problem when you send multiple requests using Ajax. All new requests after the first request (using http.open method), mantain the same value of the first request. This problem is caused by Internet Explorer use of cache.
Solution
When you call the method:
http.open
add a random variable using Math object and add it in the method's URL argument, for example:
nocache = Math.random();
http.open('get', 'page.php?url_parameter='+parameter+'&nocache = '+nocache);
http.open('get', 'page.php?url_parameter='+parameter+'&nocache = '+nocache);
In this way all the new request will have an URL parameter (&nocache) which force the browser to "refresh" the old value with the new value.
I am 
Thank you wery much !!
Thank you very much!!! You are my hero for today!!! I have killed entire day for resolving this issue..........................................
Thank you from Finland!
You rock!!!!!
Note to others: I'm using the YUI connector, so the only thing I had to do was to add the nocache to my url string for the GET before calling the asyncRequest method.
--macchick
Thanks a lot!
Muchas gracias!
Thanks bro!...
Thank you very much from Japan!
thanks from india
A saviour! Thanks!
You are a star!