I investigated the problem report related to the DSM-320 (see forums) and I now know what causes the unit to crash.
I can't say that it is really a bug on our side, but we can offer a workaround without being forced to put in some ugly hack. Bascially, the DSM-320 likes only very specific upnp:class values which we do not yet support. According to the UPnP spec this implementation is optional, so it was not a priority for the first release. However, since we now discovered that it is a blocker for the DSM-320 users we will put it on top of our list and try to bring you an update as soon as possible.