While trying to develop my first VS Addin, I am having issues in firing DTE2 events.
Basically, the DocumentOpened and LineChanged events don\'t fire for some reason
I found a different solution to this problem.
I was boxing and unboxing my DTE object before doing my event subscriptions. This ulitmately proved the culprit for me. While this wasn't your issue, it could help others who have similar issues; and is good to know so that you don't make the same mistakes I did which took an extreme amount of time to resolve.
See here: http://social.msdn.microsoft.com/Forums/en-US/vsx/thread/eb1e8fd1-32ad-498c-98e9-25ee3da71004