Cannot delete lucene locks from /tmp

In a number of our builds we're starting to see failures due to the inability to delete lucene locks from the /tmp area. We see errors like the following in our builds:

java.io.IOException: Cannot delete /tmp/lucene-18eec490b2669271cd1934bf01ac6c3b-write.lock
at org.apache.lucene.store.FSDirectory.create(FSDirectory.java:210)
at org.apache.lucene.store.FSDirectory.getDirectory(FSDirectory.java:144)
at org.springmodules.lucene.index.support.FSDirectoryFactoryBean.afterPropertiesSet(FSDirectoryFactoryBean.java:65)
at org.springmodules.lucene.index.support.FSDirectoryFactoryBeanTests.testGetObjectWithCreationWriter(FSDirectoryFactoryBeanTests.java:122)

If you'd like to see an example: http://build.springframework.org:8085/browse/MOD-HEAD-49/test/org.springmodules.lucene.index.support.FSDirectoryFactoryBeanTests

We saw this occasionally in Bamboo 1.0 but now that we've gone to 1.0.1 we're seeing it a whole lot.