Error reading node property?

I'm using Premiere Pro CS6, editing a 10 minute sequence using H.264 clips in .MOV containers. This morning I have been applying the Fast colour corrector, warp stabiliser and highlight/shadow adjustment to the clips. A small red box with a white X has appeared in the lower right corner with the message "error reading node property". What does this mean and how do I rectify it?

Thanks for your help