Threads option

[Graham90978]

Hi guys,
Im having difficulty running the multi threaded version, I wonder if you can help?
I have a 48 core server and run the command as follows:
"java -Xmx4g -jar prottest-3.4.jar -i GeneFamily.phy -all-distributions -F -AIC -BIC -s BEST -threads 20"

I have given the java compiler enough memory to run, but it only ever seems to be running on a single core, so is not running on 20 threads. Do you know if there is a workaround, or have I not ran it right?
Thank you in advance
Graham