That is what I had (and still have) installed. As I said : installing libtorrent 0.12.6 fixed the problem for me

I just updated to 1.2.0 because of the error, but it did not solve the problem.
installing libtorrent 0.12.6 fixed it (from repository / running ARCH)

I'm sorry if this is a known issue with an easy fix, but the search function just kept telling me the used words were to common. When I add a .torrent-File that creates a directory which has a dot in its name, deluge will instead create a file with that name, and keeps telling me that it couldn't co...