Logon error

I have been using this app happily for 10 months and never had a problem until today when I get the following error msg.
The system could not log you on. Make sure the user name and domain are correct etc
I asked my colleagues and they all get it to so suddenly it doesn't work for all of us. Any ideas?
The system could not log you on. Make sure the user name and domain are correct etc
I asked my colleagues and they all get it to so suddenly it doesn't work for all of us. Any ideas?