The server is having problems. Installed an extra NIC, to rule out problems with the onboard NIC, but that didn’t solve the problem. Removed the memory DIMMs now, and replaced them with two out of my desktop machine, since that had 4x4G and I don’t really use it at the moment. So they both now have 8GB internal memory. The desktop memory is Corsair Vengeance, the server memory was some value ram. Hopefully the Vengeance dimms will solve the system freezes.