Comsol Cluster Computing Problem !

Hi,
when i am about to choose three nodes of which are at the settings of comsol cluster, it says "process status" scheduling and it stucks like that. when i am about to choose two nodes, comsol cluster works smooth. what might be the reason for me not making it with three? all authorisations were tested and done accurately.

Head-Node : Windows Server 2008 R2 HPC
A Node : Windows 7
B Node : Windows 7

Head-Node + A Node + B Node : Not Working Cluster
Head-Node + A Node : Working Cluster
A Node + B Node : Working Cluster
Head-Node + B Node : Not Working

How Can I This Problem ? where exactly i need check Node and Head-Node ? Can you pls help me ? I am working solution one month problem ? But Not Working Cluster 2 more than Node Comsol.

thankyou.