It is really awkward to translate. Now it would be nice if I could do the search here because I have tried to explain this before.
This is a type of "thank you" we also use in Finland. The most common use is when the other person has invited us to his home (to a party, to a birthday or just to spend some time together). Next time we meet we want to thank him (for the evening - including food and company)... most often because it has been nice, but we thank even when it has been not so nice (then the emphasis is of course on the invitation )
Kafetzou,
the sentence you have suggested is not near what they say. They wish to thank the hosts for the last invitation and the previous party. The expression is difficult to translate.
The suggestion by Nuppu is not right.
According to the dictionaries, Cassels Swe/Eng etc., and to my knowledge it is the correct way to translate the expression as I've done. Therefore I rest my case.