outlook com addin won't release .msg file handle

I wrote a outlook com addin which will popup a dialogue box when user click on 'replyall' button to confirm whether they do want to reply to all.
However, after using it for a while, we noticed one bug:
If you open a saved .msg file and close it then you won't be able to open it for a second time.
According to Ken Slovak's answer, I will have to call ReleaseComObject method to release the handle..however, I can't seem to be able to implement this initially.
After spending hours working on it, it finally turn out that I will have to release both the inspector and mailitem objects using releasecomobject method.
And now the com addin is back to work again....