db4o and NFS problems

Strange unexpected errors running db4o on NFS file system. Everything worked fine until a mysterious exception

com.db4o.ext.DatabaseFileLockedException: Database locked: '/globalhome/gateway/queueservice3.db'
at com.db4o.internal.JDK_1_4.lockFile(Unknown Source)
at com.db4o.internal.Platform4.lockFile(Unknown Source)
at com.db4o.io.RandomAccessFileAdapter.(Unknown Source)
at com.db4o.io.RandomAccessFileAdapter.open(Unknown Source)
at com.db4o.internal.IoAdaptedObjectContainer.open(Unknown Source)
at com.db4o.internal.IoAdaptedObjectContainer.(Unknown Source)
at com.db4o.internal.ObjectContainerFactory.openObjectContainer(Unknown Source)
at com.db4o.Db4o.openFile(Unknown Source)
at com.db4o.Db4o.openFile(Unknown Source)
at org.apache.jsp.junk_jsp._jspService(junk_jsp.java:49)


This only happens on NFS directories. Changing to a local directory, the same code works fine.