I've been meaning to post a quick heads up as to what was going wrong since we solved the issue (on the Friday of the week of the last post here, sorry about the delay). .Net has a limit on the number of external connections but not internal ones. As such, when running locally all the connections could connect. Running external mean only the first 2 (the .Net default on a 32 bit Vista machine) connections were allowed. The rest received a .Net exception which the Lightstreamer library was catching and throwing it's own (which is why it wasn't trivial to find the solution.). To solve this we increased the .Net limit for external connections. In future we will move to a single connection for all subscriptions.