Thanks for the ideas. I have absolutely no clue (good at other things, not techie). Will google all those things you said and try it tomorrow. The modem and the fetch box are in different rooms - don't know why they installed it that way in the beginning but they did. I have an ethernet cable going to a dlink box thingy in the powerboard. I think that's supposed to talk to the modem in the study. What I know is that it was working and now it isn't.
Thanks again for the starting point.