The mantis importer expects to have attachments of the form <bugid>-<filename> if this is not satisfied the below exception is thrown. Jira should realy just ignore the problem if it occurs and just carrying on importing.

Error importing data from Mantis.java.lang.RuntimeException: Attachment filename 'email beacon v1.0.1.doc' does not follow the standard <bugid>-<filename> pattern at com.atlassian.jira.util.MantisImportBean.cleanMantisFilename(MantisImportBean.java:992) at com.atlassian.jira.util.MantisImportBean.importAttachments(MantisImportBean.java:934) at com.atlassian.jira.util.MantisImportBean.importIssues(MantisImportBean.java:327) at com.atlassian.jira.util.MantisImportBean.importProjects(MantisImportBean.java:782) at com.atlassian.jira.util.MantisImportBean.doImport(MantisImportBean.java:204) at com.atlassian.jira.web.action.util.MantisImport.doRun(MantisImport.java:149) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25) at java.lang.reflect.Method.invoke(Method.java:585) at webwork.util.InjectionUtils$DefaultInjectionImpl.invoke(InjectionUtils.java:61) at webwork.util.InjectionUtils.invoke(InjectionUtils.java:52) at webwork.action.ActionSupport.invokeCommand(ActionSupport.java:417) at webwork.action.ActionSupport.execute(ActionSupport.java:146) at com.atlassian.jira.action.JiraActionSupport.execute(JiraActionSupport.java:47) at webwork.dispatcher.GenericDispatcher.executeAction(GenericDispatcher.java:132) at com.atlassian.jira.web.dispatcher.JiraServletDispatcher.service(JiraServletDispatcher.java:186) at javax.servlet.http.HttpServlet.service(HttpServlet.java:802) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:252) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.jira.web.filters.AccessLogFilter.doFilter(AccessLogFilter.java:51) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:118) at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:52) at com.atlassian.jira.web.filters.SitemeshExcludePathFilter.doFilter(SitemeshExcludePathFilter.java:38) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.seraph.filter.SecurityFilter.doFilter(SecurityFilter.java:182) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.seraph.filter.LoginFilter.doFilter(LoginFilter.java:177) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.util.profiling.filters.ProfilingFilter.doFilter(ProfilingFilter.java:132) at com.atlassian.jira.web.filters.ProfilingAndErrorFilter.doFilter(ProfilingAndErrorFilter.java:25) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.jira.web.filters.ActionCleanupDelayFilter.doFilter(ActionCleanupDelayFilter.java:37) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.johnson.filters.JohnsonFilter.doFilter(JohnsonFilter.java:91) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.jira.web.filters.gzip.GzipFilter.doFilter(GzipFilter.java:64) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at com.atlassian.core.filters.AbstractEncodingFilter.doFilter(AbstractEncodingFilter.java:36) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:202) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:173) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:213) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:178) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:126) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:105) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:107) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:148) at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:856) at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.processConnection(Http11Protocol.java:744) at org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:527) at org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:80) at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:684) at java.lang.Thread.run(Thread.java:595)