Lucene lock error when starting standalone version of XE from time to time

11:00:04.497 INFO   [main] org.mortbay.util.Container.start(Container.java:74) >09> Started org.mortbay.jetty.Server@aa0a15
2009-01-08 11:00:35,969 [http://localhost:8080/xwiki/bin/view/Main/] [P1-19] INFO  .AbstractXWikiMigrationManager  - Current storage version = [0] 
2009-01-08 11:00:35,971 [http://localhost:8080/xwiki/bin/view/Main/] [P1-19] INFO  .AbstractXWikiMigrationManager  - List of migrations that will be executed: 
2009-01-08 11:00:35,971 [http://localhost:8080/xwiki/bin/view/Main/] [P1-19] INFO  .AbstractXWikiMigrationManager  -   R4340XWIKI883 - See http://jira.xwiki.org/jira/browse/XWIKI-883 
2009-01-08 11:00:35,971 [http://localhost:8080/xwiki/bin/view/Main/] [P1-19] INFO  .AbstractXWikiMigrationManager  -   R4359XWIKI1459 - See http://jira.xwiki.org/jira/browse/XWIKI-1459 
2009-01-08 11:00:35,971 [http://localhost:8080/xwiki/bin/view/Main/] [P1-19] INFO  .AbstractXWikiMigrationManager  -   R7345XWIKI2079 - See http://jira.xwiki.org/jira/browse/XWIKI-2079 
2009-01-08 11:00:35,973 [http://localhost:8080/xwiki/bin/view/Main/] [P1-19] INFO  .AbstractXWikiMigrationManager  - Running migration [R4340XWIKI883] with version [4340] 
2009-01-08 11:00:36,086 [http://localhost:8080/xwiki/bin/view/Main/] [P1-19] INFO  .AbstractXWikiMigrationManager  - New storage version is now [4341] 
2009-01-08 11:00:36,086 [http://localhost:8080/xwiki/bin/view/Main/] [P1-19] INFO  .AbstractXWikiMigrationManager  - Running migration [R4359XWIKI1459] with version [4359] 
2009-01-08 11:00:36,090 [http://localhost:8080/xwiki/bin/view/Main/] [P1-19] INFO  .AbstractXWikiMigrationManager  - New storage version is now [4360] 
2009-01-08 11:00:36,090 [http://localhost:8080/xwiki/bin/view/Main/] [P1-19] INFO  .AbstractXWikiMigrationManager  - Skipping unneeded migration [R6079XWIKI1878] with version [6079] 
2009-01-08 11:00:36,091 [http://localhost:8080/xwiki/bin/view/Main/] [P1-19] INFO  .AbstractXWikiMigrationManager  - New storage version is now [6080] 
2009-01-08 11:00:36,091 [http://localhost:8080/xwiki/bin/view/Main/] [P1-19] INFO  .AbstractXWikiMigrationManager  - Skipping unneeded migration [R6405XWIKI1933] with version [6405] 
2009-01-08 11:00:36,092 [http://localhost:8080/xwiki/bin/view/Main/] [P1-19] INFO  .AbstractXWikiMigrationManager  - New storage version is now [6406] 
2009-01-08 11:00:36,122 [http://localhost:8080/xwiki/bin/view/Main/] [P1-19] INFO  .AbstractXWikiMigrationManager  - Running migration [R7345XWIKI2079] with version [7350] 
2009-01-08 11:00:36,125 [http://localhost:8080/xwiki/bin/view/Main/] [P1-19] INFO  .AbstractXWikiMigrationManager  - New storage version is now [7351] 
2009-01-08 11:00:37,421 [Lucene index rebuilder thread] [Lucene Index Rebuilder] ERROR lucene.IndexUpdater             - IOException when opening Lucene Index for writing at /Users/vmassol/dev/xwiki/trunks/enterprise/distribution/jetty/hsqldb/target/xwiki-enterprise-jetty-hsqldb-1.8-SNAPSHOT/jetty/work/Jetty__8080__xwiki/lucene 
org.apache.lucene.index.CorruptIndexException: failed to locate current segments_N file
        at org.apache.lucene.index.IndexFileDeleter.<init>(IndexFileDeleter.java:207)
        at org.apache.lucene.index.IndexWriter.init(IndexWriter.java:722)
        at org.apache.lucene.index.IndexWriter.<init>(IndexWriter.java:502)
        at com.xpn.xwiki.plugin.lucene.IndexUpdater.openWriter(IndexUpdater.java:337)
        at com.xpn.xwiki.plugin.lucene.IndexUpdater.cleanIndex(IndexUpdater.java:466)
        at com.xpn.xwiki.plugin.lucene.IndexRebuilder.rebuildIndex(IndexRebuilder.java:187)
        at com.xpn.xwiki.plugin.lucene.IndexRebuilder.run(IndexRebuilder.java:160)
        at java.lang.Thread.run(Thread.java:613)
2009-01-08 11:00:37,425 [Lucene index rebuilder thread] [Lucene Index Rebuilder] ERROR lucene.IndexUpdater             - Writer not open and closeWriter called