Upgrading ancestry for CVS changeset fails on 2.6.1

2011-07-06 15:13:50,135 INFO  - Starting upgrade task upgrade-changeset-ancestry-3 on platform
2011-07-06 15:14:13,955 WARN  - TopologicalOrderChangesetIterator.addCsAndParentsToFront: Cyclic Ancestry Detected: [][retail01_1:buildman:19870123004631(nchai101901:nchai:20011110014955,), ]
2011-07-06 15:14:34,692 WARN  - TopologicalOrderChangesetIterator.addCsAndParentsToFront: Cyclic Ancestry Detected: [retail01_1:zliu:20011010221628(nchai101901:nchai:20011110014955,), ][nchai101901:nchai:20011110014955(retail01_1:zliu:20011010221628,), retail01_1:buildman:19870123004631(nchai101901:nchai:20011110014955,), ]
2011-07-06 15:14:54,493 WARN  - Infinite Loop detected during upgrade of ChangeSet ancestry: retail01_1:zliu:20011010221628 pos:null; parents:[nchai101901:nchai:20011110014955; pos:null;]: breaking: position may be incorrect for this ChangeSet
2011-07-06 15:14:54,495 ERROR - problem with initial scan
com.cenqua.fisheye.rep.DbException: Error during upgrade task upgrade-changeset-ancestry-3 on platform
	at com.cenqua.fisheye.rep.impl.BaseUpgradeTask.upgrade(BaseUpgradeTask.java:67)
	at com.cenqua.fisheye.cvsrep.cache.CachedCvsRepositoryUpdater.upgrade(CachedCvsRepositoryUpdater.java:293)
	at com.cenqua.fisheye.cvsrep.cache.CvsHistoryChangeDetector.doRunOnce(CvsHistoryChangeDetector.java:117)
	at com.cenqua.fisheye.cvsrep.cache.CvsHistoryChangeDetector.ping(CvsHistoryChangeDetector.java:54)
	at com.cenqua.fisheye.cvsrep.cache.CachedCvsRepositoryUpdater.pingSlurp(CachedCvsRepositoryUpdater.java:279)
	at com.cenqua.fisheye.cvsrep.CvsRepositoryEngine.doSlurp(CvsRepositoryEngine.java:68)
	at com.cenqua.fisheye.rep.RepositoryEngine.slurp(RepositoryEngine.java:390)
	at com.cenqua.fisheye.rep.ping.OneOffPingRequest.doRequest(OneOffPingRequest.java:25)
	at com.cenqua.fisheye.rep.ping.PingRequest.process(PingRequest.java:66)
	at com.cenqua.fisheye.rep.RepositoryHandle.processPingRequests(RepositoryHandle.java:132)
	at com.cenqua.fisheye.rep.RepositoryHandle.queuePingRequest(RepositoryHandle.java:122)
	at com.cenqua.fisheye.rep.ping.PingRequest.run(PingRequest.java:33)
	at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
	at java.lang.Thread.run(Thread.java:619)
Caused by: java.lang.NullPointerException