It generally means that your set top box is not provisioned, ie not set up to use. If you have been using it with zero issues you will need to first reboot everything and if it does not work then you need to ring vodafone as it seems from others in this forum that they often are mixing up the serial numbers on boxes and may have cut your one off by having it associated with another persons account that has either not paid bills or shut their account down.
1) They can, once a show is recorded, disappear very fast, from 3 days onwards, and you will get no prompt that it has or will delete.
2) If you have a series on series record the above happens with the earlier recorded content even if the show is still on and you are recording current episodes.
3) If you have a show on "series record" it is almost impossible to know that you have put it on "series record", so you might press the "record" button again - if you have actually already done that, it will immediately delete all that series content without any "do you really want to delete" warnings, it just does it. I've been burn't several times from that one!
4) If you accidentally "double tap" the record button when setting up a series record, or to record a show, it will delete it as it also doesn't ask if you really want to delete or stop the recording option on that show.
I guess the only safe option is to make sure you watch whatever you record within three days if you really really want to watch it. You can protect some shows, but it only does it episode by episode if you have a series of say 20 episdes you will need to do that for each of the 20. It also has a limit (not sure how many) so you cannot protect too much.
Hope that helps. Just answering as it seems hard to get a Ninja to answer.