There's no convenient time for software crashes, is there ?
Does the application open correctly offline ? Try exporting as *.L5K and re-creating the *.ACD.
Any chance you're running in a VM with autoprotect snapshots ?
Edit: It's gotta be v19 with an L7x controller, and obviously you're online. Probably a big process-control application.
The controller's still running, isn't it ?