Here's a cheat sheet of how to fix crashing ArcMap. An ArcMap "crash" is when ArcMap abruptly closes, or closes with a popup referencing an application error.
Stop going down the list when things are working again. Good luck!
- If you get crashes on one mxd or dataset the mxd or data may be corrupted. Copy your layers, start a new blank MXD, paste to the new data frame. If it's a complex MXD that would take a lot of time to rebuild from scratch, try to repair the mxd with MXD Doctor. Back up your data and try to rebuild a dataset that is making things crash.