IE 9 version having trouble with browser cookies

I am having weird problem with setting up the cookies on IE9 for certain users. I am sett开发者_StackOverflow中文版ing up the cookie on on the parent domain with ".mysite.com" on x.mysite.com, I am expecting it to be read from y.mysite.com. The problem is on all the browsers it works but IE9 on certain machines it never works. I tried setting up our staging machines and it worked perfectly but somehow in production it breaks for some users.

We have a hybrid environment where the cookie is set up by the .net environment(x.mysite.com) and the java environment(y.mysite.com), we are using persistent storage for saving the session between different environments.

I have tried debugging the problem I do see the cookie is set from x.mysite.com but never sent from the browser for y.mysite.com.

The cookie name is prefixed with "www" eg. "wwwXYZ" Doesnt seem like a server issue, but something how IE is handling it, Am i doing something wrong or others too having the same issue.