Hey Dan,
What you are talking about, is it that the autothrottle don't seem to react. If so, that happens to me sometimes. so when that happens I have to switch off the IAS setting and turn it on again. Also I have found I have to turn off both the IAS setting and the autothrottle to get manual control again. something don't happen on other panels. Well the A345 does the same so it's perhaps a Airbus/Mitchell thing. Haven't seen it happen on other of this panels