While previewing my report i got a “An unexpected error occurred in Report Processing. Index was outside the bounds of the array.”. I couldn’t my out of bounds index anywhere.
The Index error exception popped up when i added a new field to the report and hit “View Report”. Apparently the report caches these columns in Preview mode.
I hit the Refresh button in Preview mode and the report magically appeared. Now clicking View Report works also.
So a little hint for all you out there, this one you forget o so soon.