I use YUI 3.3.0pr3 to make cross window/domain communication.
In page A (a.com), user clicks login link it use window.open() to show page B (b.com).
After validation, page B creates an iframe (a.com) as proxy to execute parent.opener.YUI().use("node", callback).
All IE versions failed to to execute the callback, but other browsers does work well.

Demo :
http://josephj.com/lab/yui3-opener-proxy-bug/open.html

After checking the latest code, I find the callback will be set to null because it's not a function but an object.
I can solve my trouble as following:
$ diff yui-debug.js yui-debug-fix.js
614c614
< if (Y.Lang.isFunction(callback)) {
---
> if (Y.Lang.isFunction(callback) || Y.Lang.isObject(callback)) {
Not sure if this is the correct way to do.

The okay demo:
http://josephj.com/lab/yui3-opener-proxy-bug/open-fix.html