Windows 2003 NLB Not Routed Through Cisco Switch

I am having the exact same problem to the issue described here:
https://www.experts-exchange.com/questions/23115937/Windows-2003-NLB-not-routed.html

Basically, we have set up MS NLB for two Windows 2003  webservers on a 192.168.8.x range.  The server addresses are 8.2 and 8.3, and the NLB address is 8.4.  We are using multicast, as the servers must be able to communicate with one another.  I have a Cisco Catalyst 3550 L3 switch, which routes traffic using a single VLAN set up with a primary .8.x address and secondary addresses for .10.x and .12.x.  I can ping both servers from any of the above subnets (because their gateway is the L3 switch), but I can only ping the NLB address from the 8.x subnet.  I need this to communicate across all of the subnets on the above VLAN.  The solution given in the above thread was to put the NLB in a separate VLAN.  Could someone explain what he meant specifically, or how I can solve this issue with the equipment I have?  Do create another VLAN on the L3 switch with a different subnet (say, 192.168.20.1) and set the NLB address to 20.x?  Any help would be much appreciated, and specific commands or instructions would be a bonus.

Thanks in advance.