You're lucky they got an application hang or access violation error. The more frequent complaint is about unrecoverable data.
Shared workbooks come up fairly in the Excel TA-and you're not going to like the advice. The Shared Workbook feature (IMHO) has long been one of the buggiest features in Microsoft Excel. Workbook corruption is regarded as inevitable by many of the regulars in this TA-and most other tech support forums you care to visit. FWIW, Microsoft addressed some (but not all) of the underlying causes in the Excel 2007 SP1 update.
If you really need to have more than one person simultaneously accessing and changing the data-then please consider using Access. It has a robust multi-user capability. Excel, I am sorry to say, does not.
Fellow expert Patrick Arnold-Baker (patrickab) advises the following work-around to facilitate access by multiple people. First make the file single user (i.e. turn off the Share Workbook feature). Second edit everyone's user profile in the Tools...Options...General menu item-put the person's name and telephone extension number in the "User Name" field. Then whenever you attempt to open a file that someone else is using, a dialogue box will pop-up telling you who is the current user-and it tells you their telephone extension number! The new user can either call the current user or else open the file as read-only.
