Were you able to create a reduced reproduction of the issue? The _proxy handler should be receiving an event facade (e) that has passed through the DOMEventFacade (IE version) constructor, which *really should* populate e.target. I'm curious about the root of the problem.

I got same problem, you can debug it in ie10 (windows 8 rc) in ie7 compatibility mode or in ie7 (on windows xp). e.target is undefined, so target.getData(nodeDataKey) fails. I got this error in mojito, using binder - ie7(ie8 with all service packs not) fails.

I got same problem, you can debug it in ie10 (windows 8 rc) in ie7 compatibility mode or in ie7 (on windows xp). e.target is undefined, so target.getData(nodeDataKey) fails. I got this error in mojito, using binder - ie7(ie8 with all service packs not) fails.

Can you update the test url to an endpoint? That link points to the root of a branch.

Just got this error. It takes much time to reproduce it. I've experimented that time, so it takes some time to remember.
I've updated https://github.com/focuzz/mj-defer-demo , but it's not enough to reproduce.
After you pull and start this demo (root url - '/'), you'll get in IE7 error I've described there https://github.com/yahoo/mojito/issues/262
Then, I've tried to fix this error in this way:
in mojito/lib/app/autoload/output-handler.client.js on line 101,
I replaced
if (meta.http.headers['content-type'] && meta.http.headers['content-type'][0].indexOf('application/json') === 0)
with
if (meta.http.headers['content-type'] && Y.Lang.isArray(meta.http.headers['content-type']) && meta.http.headers['content-type'][0].indexOf('application/json') === 0)
This helps with initial error in IE7, but, if you click on any link in menu in IE7 after this - you'll get error described above.

If you'll have any questions - feel free to ask.