Bugzilla import fails

Cryptic error message after importing components.

http://confluence.atlassian.com/display/JIRA/Importing+Data+from+Bugzilla doesn't bear a lot of similarity to the actual import process... eg. there is no Maximum issues and failues option anywhere along the line.

Log file contains the following stack trace:

2011-09-14 11:45:22,632 ERROR - Unexpected failure occurred. Importer will stop immediately. Data maybe in an unstable state
java.util.UnknownFormatConversionException: Conversion = ' '
at java.util.Formatter.checkText(Formatter.java:2503)
at java.util.Formatter.parse(Formatter.java:2485)
at java.util.Formatter.format(Formatter.java:2414)
at java.util.Formatter.format(Formatter.java:2367)
at java.lang.String.format(String.java:2769)
at com.atlassian.jira.plugins.importer.imports.importer.impl.FileImportLogger.log(FileImportLogger.java:44)
at com.atlassian.jira.plugins.importer.imports.importer.impl.DefaultJiraDataImporter.importProject(DefaultJiraDataImporter.java:572)
at com.atlassian.jira.plugins.importer.imports.importer.impl.DefaultJiraDataImporter.doImport(DefaultJiraDataImporter.java:275)
at com.atlassian.jira.plugins.importer.imports.importer.impl.ImporterCallable.call(ImporterCallable.java:25)
at com.atlassian.jira.plugins.importer.imports.importer.impl.ImporterCallable.call(ImporterCallable.java:14)
at com.atlassian.jira.task.TaskManagerImpl$TaskCallableDecorator.call(TaskManagerImpl.java:359)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:303)
at java.util.concurrent.FutureTask.run(FutureTask.java:138)
at com.atlassian.multitenant.impl.DefaultMultiTenantManager.runForTenant(DefaultMultiTenantManager.java:61)
at com.atlassian.multitenant.juc.MultiTenantExecutors$WrappedRunnable.run(MultiTenantExecutors.java:160)
at com.atlassian.jira.task.ForkedThreadExecutor$ForkedRunnableDecorator.run(ForkedThreadExecutor.java:249)
at java.lang.Thread.run(Thread.java:662)