For OneCare the appropriate place will always be in these forums, based on they type of problem you are having.
Those of us Moderating here are already heavily involved with MSE, but we're also still spending time here as well as a few others who lurk here and regularly answer questions too.
Since OneCare will continue to be supported by Microsoft until late 2010, we assume these forums will also remain until that time, though it's always possible they may move again. But if they do, I'm sure we'll all get sufficient notice as happened the last time they moved.
Rob