Thank you Markoz, seems to work now. My mistake was pressing INSERT twice after entering 8/N. I thought I have to get the INSERT light off before I can start inserting W/E fix. Or, in other words:

My incorrect procedure:

1. 8/N
2. lat
3. INSERT
4. INSERT
5. 6/E

-> Won't work

1. 8/N
2. lat
3. INSERT
4. 6/E
5. lon
6. INSERT

-> Works.

Anyways, thanks for the help, very kind or you. :)