I've imported data from jira 1.4.1-#21 with success.
When I try to export, I get :

2003-05-13 22:44:11,175 ERROR [web.action.util.ExportAll] Exception occurred exporting: com.atlassian.core.AtlassianCoreException: Error in action: com.atlassian.jira.action.admin.DataExport@1c1cfc1, result: error
Error exporting: java.io.IOException: The character '' is an invalid XML character
com.atlassian.core.AtlassianCoreException: Error in action: com.atlassian.jira.action.admin.DataExport@1c1cfc1, result: error
Error exporting: java.io.IOException: The character '' is an invalid XML character
at com.atlassian.core.action.ActionUtils.checkForErrors(ActionUtils.java:53)
at com.atlassian.jira.web.action.util.ExportAll.doExecute(ExportAll.java:37)
at webwork.action.ActionSupport.execute(ActionSupport.java:114)
at webwork.dispatcher.GenericDispatcher.executeAction(GenericDispatcher.java:113)
at webwork.dispatcher.ServletDispatcher.service(ServletDispatcher.java:161)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at com.opensymphony.module.sitemesh.filter.PageFilter.parsePage(PageFilter.java:129)
at com.opensymphony.module.sitemesh.filter.PageFilter.doFilter(PageFilter.java:61)
at com.atlassian.jira.web.filters.SitemeshExcludePathFilter.doFilter(SitemeshExcludePathFilter.java:35)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at com.atlassian.core.security.SecurityFilter.doFilter(SecurityFilter.java:170)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:213)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at com.atlassian.core.security.LoginFilter.doFilter(LoginFilter.java:191)

[... etc ... ]