I have been using Arcview 10.0 to develope multiple map layouts (data driven pages) for the last year. I have had no problems until this week. Suddenly, whenever I refresh my DDP, it changes my layer coordinate system to a system that is not used in my map, is not referenced anywhere, and has never been a part of my map. It also causes my map to loose all it's data since the new system is nowhere close to the original. I started all over, using data with the same coordinate system and it still happens. If I change the layer system back to the correct one, my data returns and all is pretty, but I can't move from page to page. If I refresh, it happens all over again! Please help me figure out what is happening!