Same problem, and very sure it was ok 2 days ago.
This is similar to the problem that still hasn't been fixed in the search results where caches are listed by distance from the users home instead of the refeernce coordinates or cache.
I just noticed this too when I went to 'Will Attend'. Normally, I'd use the 'add to calendar'. Waiting for its return. I do wish the developers would stop breaking stuff.