Dell PowerConnect 6024 and windows load balancing

I'm trying to set up Windows Network Load Balancing but for some reason the cluster IP cannot be seen from outside network. The two cluster nodes are Dell PowerEdge 1950 connected with its dual port NICs to two Dell PowerConnect 6024. As per Microsoft instructions I've set up the cluster in multicast mode and turned on IGMP snooping on the switches. So my question is, are there any known issues with WLBS and Dell switches or it's just missconfiguration? I'll appreciate any answer on that topic.