Just wanted to offer an additional suggestion. I run Win7 in vmware Fusion on my Mac. There seems to be a bug related to allowing the multicast packets the repeater uses all the way in to the VM, even in bridged mode. I was able to work around this by using Wireshark, a network sniffing program, on my Win7 VM. If you tell it to do a packet capture, by default, it tries to do so in promiscuous mode, which means listen on the network interface for all traffic, not just traffic intentionally targeted for the machine it's running on. This requires administrative access at the host (Mac) level, which means your Mac will prompt you for your password at that point to let Fusion enable promiscuous mode on the network interface. Give the password, now multicast should be making it to the guest VM and your RadioRA software successfully. I'm able to talk to repeaters reliably now when doing so from a VM over hard wired network to the host Mac.
Second issue that may affect you, depending on the underlying network infrastructure, is IGMP snooping at the network switch level not including all the necessary switch ports in the multicast group the Lutron devices and software use. I found it easiest to just disable IGMP snooping on the VLAN where the Lutron equipment lives. You can do so on Cisco switches, for example, on a per-VLAN basis, using "no ip igmp snooping vlan ##" where ## is replaced with the relevant VLAN number.