Don't blame users for JIRA exceptions: It is likely that the import was not correctly configured.

My FogBugz import failed and this is shown on the top of the page:

FogBugz import completed with errors
The importer has completed with some errors. You can find the errors in the logs below by searching for lines which begin with FAILED. It is likely that the import was not correctly configured.

The text "It is likely that the import was not correctly configured." should read "It is possible that the import was not correctly configured.". But really, it should check what type of exceptions were generated and handle it accordingly. Ideally a link to Atlassian's own JIRA installation searching on the exceptions would be user friendly and relatively easy to implement.

The exception I actually got was

[08:59:50] Only new Issues will be imported
[09:02:08] FAILED: Unexpected failure occurred. Importer will stop immediately. Data maybe in an unstable state
[09:02:08] com.atlassian.jira.external.ExternalRuntimeException: java.io.UnsupportedEncodingException: geostd8
at com.atlassian.jira.external.ExternalUtils.getTextDataFromMimeMessage(ExternalUtils.java:922)
at com.atlassian.jira.imports.fogbugz.transformer.CommentTransformer.transform(CommentTransformer.java:48)
at com.atlassian.jira.web.action.util.DatabaseConnectionBean.queryDb(DatabaseConnectionBean.java:271)
at com.atlassian.jira.web.action.util.DatabaseConnectionBean.queryDb(DatabaseConnectionBean.java:252)
at com.atlassian.jira.imports.fogbugz.transformer.IssueTransformer.transform(IssueTransformer.java:208)
at com.atlassian.jira.web.action.util.DatabaseConnectionBean.queryDb(DatabaseConnectionBean.java:271)
at com.atlassian.jira.web.action.util.DatabaseConnectionBean.queryDb(DatabaseConnectionBean.java:252)
at com.atlassian.jira.imports.fogbugz.FogBugzDataBean.getIssues(FogBugzDataBean.java:65)
at com.atlassian.jira.imports.fogbugz.FogBugzDataBean.getIssuesIterator(FogBugzDataBean.java:70)
at com.atlassian.jira.imports.importer.impl.DefaultJiraDataImporter.importIssues(DefaultJiraDataImporter.java:430)
at com.atlassian.jira.imports.importer.impl.DefaultJiraDataImporter.doImport(DefaultJiraDataImporter.java:120)
at com.atlassian.jira.imports.importer.impl.ImporterThread.run(ImporterThread.java:21)
Caused by: java.io.UnsupportedEncodingException: geostd8
at sun.nio.cs.StreamDecoder.forInputStreamReader(Unknown Source)
at java.io.InputStreamReader.<init>(Unknown Source)
at com.sun.mail.handlers.text_plain.getContent(text_plain.java:64)
at javax.activation.DataSourceDataContentHandler.getContent(Unknown Source)
at javax.activation.DataHandler.getContent(Unknown Source)
at javax.mail.internet.MimeBodyPart.getContent(MimeBodyPart.java:603)
at com.atlassian.jira.external.ExternalUtils.getCleanedContent(ExternalUtils.java:956)
at com.atlassian.jira.external.ExternalUtils.getTextDataFromMimeMessage(ExternalUtils.java:938)
at com.atlassian.jira.external.ExternalUtils.getTextDataFromMimeMessage(ExternalUtils.java:918)

Which is JIRA missing an encoding and not a configuration problem and not a user error. It's also something JIRA could easily clean up and present to the user in a friendly way (i.e., "Case ID's x, y, and z where not imported because their attachments use encoding geostd8 and that encoding is not supported. To search Atlassian's support for information on adding adding this encoding click here."