I had this once before, I think it was caused by one of the assets. Try moving the assets into a different location on the HD and re-open the project, DVDSP will moan at you for having 'lost' the assets, but then you can re-link to the assets in their new location one by one to see which one/s cause the problem.

I'm pretty sure that's how I solved it. Might involve re-rendering/importing the corrupted asset from it's original source afterwards.