Unfortunately that message is usually associated with a file corruption.
If you contact your VAR they might be able to restore it to a previous state.
For future reference, file corruption usually occurs when saving to a networked drive and the connection cuts out whilst doing so. So is worthwhile double checking your connection.
Thanks that's exactly what it was. We have the ability here to restore files so we went back in time and restored it. At first it didn't want to open but a half hour later it did successfully. IT guy thinks maybe an update or something was interfering with it.