Tickets "closed" when not wanted

[GeirL]

When we receive a ticket, we often add a note to the ticket, or set it to "pending", or forward a message to a recipient. But in the latest version of OTRS, every time we do this, the ticket automatically gets the message that it's closed, and send that message to the one that opened the ticket. (But it's not fully closed and removed from the status view list.)
This didn't happen in the earlier versions.
See attached image for an example. (Some is in Norwegian, but "er avsluttet" means "is closed")
I've gone through the settings, but can't figure out what's wrong.
Any help appreciated!

[GeirL]

A little update: In th Admins SysConfig, under Ticket:Frontend:AgentTicketForward###StateDefault, it seems to be impossible for me to change the default value "Closed successfully" no matter what I try to change it to. (See enclosed image.)
It may or may not be related to the original post...

Any suggestions? (We use OTRS patch release 18)