Daaan, This KnowledgeBase article seems to address the issue you're seeing.
Blake, awesome! I'm on holiday for about a week (checking forums.ni.com on holiday, that's bad......) so will try this when I'm back. Thanks very much.
For future reference: the knowledge base article Blake linked to did indeed fix the problem.
Does anyone know where this Knowledge Base article has gone? The above link is dead.
See this article HERE