problem encountered in creating partition for hexahedral mesh

Dear Friends

I am using metis to partition my hexahedral mesh using mpmetis command. My mesh file is as in the following
Number_of_cells(N) element_type(3, for hexahedral)
node11 node12.. ... node18
.............
.............
nodeN1 nodeN2..... nodeN8

however after execution the command ./mpmetis, it shows '*** Meshes with more than one balancing constraint are not supported yet'.
Can you please help me to get rid of this problem...
regards
Singha