inconsistent test suite performance

I see inconsistent performance running the JBM test suite. Here I have 2 builds on the same physical machine (windows), using local disk storage so environment should be pretty stable.

The mysql database is shared but I doubt it is the culprit.

I run the test suite with the following options:
property( name: "functional.tests.database", value: dbname )
property( name: "stress.tests.database", value: dbname )
property( name: "clustering.tests.database", value: dbname )
property( name: "test.target", value: "report" )
property( name: "test.bind.address", value: properties["env.MYTESTIP_1"] )
property( name: "jboss.messaging.groupname", value: properties["env.BUILD_TAG"])
property( name: "jboss.messaging.datachanneludpaddress", value: properties["env.MCAST_ADDR"] )
property( name: "jboss.messaging.controlchanneludpaddress", value: properties["env.MCAST_ADDR"] )

Are there any other options I can add to increase isolation from other processes in the same LAN?
Would you be able to look at these 2 builds and based on the logs, say why is the first one taking longer and eventually timeout?
http://hudson.qa.jboss.com/hudson/view/SOA-Release/job/soa-jbm/163/
http://hudson.qa.jboss.com/hudson/view/SOA-Release/job/soa-jbm/164/