The Killing Floor hasn't been supported in years and that's unfortunate.
There are a couple of alternatives.
Kenneth Strom make a alternate mutli-ship host ad-don called Tactical VCR. I ran a couple of games with it and it was stable. You can find it in his FTP area here.
ftp://ftp.circus-maximus.com/pub/VGAPla ... nethStrom/
The author of PHost Stefan Reuther has also made a native multi-ship combat add-on for PHost, however it's in beta and we've had a tough time trying to get enough people to do a test game. I'm not sure if he's done any new work on it in the last couple of years.