ubvec not work, can i get some suggestions

recently i use the parmetis in my DSMC program
it works very well except the multiple load balance
i want the (max load - min load)/(average load) can be kept around 1%
so i set the ubvec as 1.005 for two load parameters
but it didn't work and load imbalance kept around 10%
the total particle number is about 2 million and divided by 8 processes. particle number per element ranges 30~300
i doubt what can i do to improve the load balance

by the way, i had used gpmetis program of metis in windows7, if i set the -nooutput, it's ok. but gpmetis.exe will stop
in the output without that flag. is there anyone has the same experience.