I have a database I support and several times in the past 2 weeks (never before) I have had the database give an error of "The Microsoft Jet database engine stopped the process because you and another user are attempting to change the same data at the same time"

I cannot get any of the data out of the DB once this error occurs and I have a very frustrated team of people that are trying to enter data in. Can anyone help me understand why it is happenning, how to stop it and MOST IMPORTANTLY, how to get into the broken DB to get the records out?