To address some concerns about the hotfix, we have some news.
If you are experiencing the issue with opening emails and email sticking in queues, if related to application of fixes as described by this blog post, here is what you can do:
If you are on Exchange 2003 SP2, you can call support services and ask for a hotfix referenced in KB article 934450; this article is not even published yet (we are working on it) - but the hotfix is available from our support organization at this time.
If you are on Exchange 2003 SP1 and need a post SP1 hotfix for this issue, we do not have that fix ready yet. At this time I do not have the exact information as to when it will be ready, other than it is being worked on.
Other than that - the removal of Exchange hotfix that caused this problem will resolve the issue too, as many of you have already posted about.