There is an updated list available of paths and tracks in the Cairngorm National Park damaged during Storm Frank, for those still planning, or those who would like to check their planned route is still passable...
http://cairngorms.co.uk/park-authority/advice-guidelines/outdoor-access-advice/
Scroll down for the list.

Thanks for this useful information, Louise. Hopefully some paths will be repaired by Challenge time, but bridges tend to take a lot longer.