Heh, its a little bit like talking to myself, but seems like the prob is solved.
Checked msec settings on my laptop. There was no rule about /mnt/fileshare so I made one. It was possible to save files now, but with incorrect ownership, ie user/user, not user/fileshare. So I went to look for msec settings in server. It appeared that there was msec rule for /fileshare, but with SGID flag missing. So I amended that and now everything works like it should.
Lets see if this is permanent success or it will disappear as soon as I have to reboot the client.
Anyway, thanks, Gowator, your hint about msec was invaluable!
Wahur, can now have a life, hopefully, at least for vacation :-))