Dispose those objects!
If you’re using the SharePoint object model anywhere, make sure that you dispose any objects that you create (not those that the SharePoint object model creates for you, like calling GetContextWeb()).
These objects have a small memory footprint visible to the Garbage Collector, but a large amount of unmanaged resources …
I’m no Scott Woodgate, but I think I know a fair amount about BizTalk. However, it seems that I never recognized what the Listen shape actually does (you don’t see this mentioned very often btw.). Turns out that this little shape can solve many of the problems we’re currently having, mainly correlation issues, like situations …