I had something similar happen, Christian. I managed to get it downloaded by tinkering with the network settings (bottom right corner of the server browser), but never really made sense of what the problem was. The main thing I did was turn the bandwidth up.
No, there are some issues with "get mod" (Vmod download). It's trail and error at the moment. Some times it works, some times it doesn't. Network settings should be 256kbs on the client side. Setting a higher number has no effect.
"Get Missing Content" is from external links and is not limited by the 256kbs.