Guys,
There was no key change in these last days.
What did happen was that Cablecom changed some channels from SD to HD permanently and so you have lost those old channels and need to do a new network search.
If you get a DM500 or clone you have lost some channels forever as they do not broadcast in SD any more.
Assuming that you have a HD receiver and in order to get the correct data to your connection you can go to
http://www.upc-cablecom.ch/en/support/tools/setup-id/ and put your address in.
In result you will get a full set of data that allows you to scan the network in your location and so, get all the channels.
Please, never mistake a simple channel change to new keys and never, never, say that some channels work with one key and others with other key.
Regards,
KK