Nope, use vinilla 1.8.1 all the way all the time.
Who else uses multiplay and has this issue? As i've seen a few posts regarding no ore and multiplay.
I do, I think it has to be an issue with multiplay but with no Confirmation from the mod support its hard to tell. Might be safe to assume they use some kind of Hard coded launcher and unless its included in THERE system it wont get enabled.