Well that doesn't say it is rustock-c at all just Win32.Ntldrbot, so it is just another point in the no standard naming of virus/malware.
The other two detections also appear to be heuristic malware.gen and viper.Suspicious.
So this appears to be a new variant and not rustock-c otherwise there would have been more detections on the other scanners by signature. So yes it would appear that avast doesn't detect this 'new' malware variant, but I would say the jury is out on this being rustock-c.