Question : Lotus Notes User Can't Open Client

I am not that familiar with Lotus Notes, so please bear with me. User has Notes version 5.0.4a. Problem is with two users, when they start their notes client, they get the following error "This database is being used by someone else. In order to share a notes database, all users must use a Domino server instead of a file server". Researching this error, I find very little and most of it is related to the whole notes database and not individual users.

All other users have a different problem. They can log in, but can't just click the mail icon. If you go and open their database manually, then they can access their mail.

So I don't know if these problems are related, but really I'm concerned about the first issue as it is preventing them from getting to their mail totally. I have restarted the notes server and that didn't help.

Answer : Lotus Notes User Can't Open Client

About first issue:
That happens when someone opens a server's NSF (Notes database) using file system (e.g. Windows explorer) instead of Notes client's open database dialog.
But that should've stopped when you restarted your server, so it seems like something else is locking your files. Have you installed an anti-virus on your server recently?

About second issue:
Have you tried to remove and then again add mail db bookmarks from their notes clients?