Yours sounds to be the same as mine Joanus, my arum lily suffered badly in the bad winter conditions of 2010.
Last year there were one or two leaves and this year even more, though nothing like how it was. I think most of the plant died in the cold and damp, but a small part remained alive, this is now growing okay and if we have milder winters will be a strong plant again in a couple of years.

My one is the same hopfully it will recover ,I have potted up some just to be on the safe side and have fed the parent plant just to try and boost its flowering this year .

I may be shouted down now, it might be the moisture and nutrient levels, we have had a lot more rain this year so it could be sommat to do with that. We had a mild winter, when the flowering buds may have formed, then a hot spell where it held on to them, then it became cold and wet, which stopped the flowers buds from growing, during the past few weeks, with all the warm but wet days, it decided to throw up the flowers no matter what. i had one growing in a border for a few years with similar problems, then when I moved it to my boggery, A run off from a neighbouring septic tank, it flourished.