Well, I was hoping that there would be something running under it and possibly svchost as I can't see why System would be using concurrent connections.
I was also hoping that there would be a process that was identifiable as one that would be using up connections. Unfortunately that doesn't appear to be the case.
I guess it is down to trying to find out why the collision on port 120 (Spamihilator from your original post) I don't know how spamihilator works or if it uses multiple connections.
Windows Mail is the new Outlook Express isn't it ?
If so there are lots of hits on a google search for the error 0x800CCC90, mostly about OE, I had a quick look but I didn't find anything relating to concurrent connections, etc.
You could always increase the current connections limit, but I suspect that it may fall over at the new level.