Just today, Similar scenario occurred for all the users at my end as well. System DSN for a DB somehow got changed to master on that server for al teh users in domain. Now, Though I am able to change the DSN back to the db manually on my local machine, but it is still a chaos among all other users. I checked with the DBA and there was no change to the database or the server hosting the database. Please keep posted if someone finds the reason and how do you deal with such situation.