Cluster computing got stuck :external progress scheduling

Hi,Ihave recently setup a cluster and i had comsol 4.3 on the head node,and i had the installation forder shared,
model working directory shared.
However,when I am trying to submit a batch job,using the cluster model in the user guide libarary,it happened to be stuck during "external progress :scheduling"(I found it in the .mph.log file).
And situation is,if I select only one node,the head node,comsolclusterbatch.exe progresses perfect and responded correctly.I select the second node,the compute node,the comsolclusterbatch.exe is effective again and returned the result correctly.
And if I set the node=2 both into working,a job requiring two nodes submitted to the HPC job manager,on both two computer nodes the comsolclusterbatch.exe appeared,comsuming some of memory,ca 60M,but neither of them is comsuming any CPU,and the progress is 0.
I found the log stuck at "external progress 1 :scheduling"
It's very strange that comsol failed to work parallely on two nodes.
I am running windows HPC 2008 R2 on the head node and the compute node.
The headnode have an i7 CPU,and the compute node have a AMD B28 cpu. Both the memory is 16G.

looking forword to your reply