Website going down every night

We are getting errors every night at around 3:00 AM giving “Error Establishing Database Connection” – it doesn’t stay long, however, it’s affecting our international customers mainly where it’s 9:00 AM and they’re working on the system. It just so happens that “Snapshot” is doing backups around that time. I don’t see any error logs on this either. Is there any way to ell what’s going on? Here’s a shot of the facebook message I received from our customer: http://www.screencast.com/t/tZU1qawAv98