With JBoss6' snapshot as of 2010-12-14 (also with previous ones, but after CR1), there are ObjectStore directories created outside of jboss.server.data.dir where they belong to. Aside from that one of them looks very suspicious having the name "PutObjectStoreDirHere".
In deploy\transaction-jboss-beans.xml the objectStoreDir is configured with default of <property name="objectStoreDir">${jboss.server.data.dir}/tx-object-store</property>; system-property jboss.server.data.dir is set to a specific directory (not sure if this is neccessary for the bug to occur.

The following directories and files are created:
In jboss.server.data.dir (correct):

In run-directory (incorrect):

Expected behavior: all data created under directory configured with objectStoreDir.