File already Open?

[srizki]

I was in network file yesterday as read-only, and I left my computer on as usual, and today my co-worker tried to open the same file, and he is getting a message, that he is in that file and it will open as read only. I told him that I was in his file as read only and left it open, now he thinks that the message he is getting is because I left the file open and when server uploaded this file overnight, program messed it up and thinks that file is still open.
I know that is not the reason for that, but what is the reason for getting message that file is open while it is not.

Thanks