User with id -1 not found

When trying to import a CSV with a batch job (scheduled task, with FTP), the following error appears: 

"User with id -1 not found"

There is a bug reported in the knowledgebase and the resolution is to upgrade to version 2.1 or later. We are using 3.0.3...

What can be the cause? Find below the log:

[2014-09-11 09:51:28,875] Rollback transaction #145 in thread 51 due to com.rb.core.services.event.TriggerException: User with id -1 not found
[2014-09-11 09:51:28,890] ===> Error in thread ajp-apr-8009-exec-5 at 09/11/2014 09:51 AM
[2014-09-11 09:51:28,890] com.rb.core.services.event.TriggerException: User with id -1 not found
	at com.rb.core.services.event.impl.ScheduledImport.trigger(ScheduledImport.java:45)
	at com.rb.core.services.event.TriggerRunner.runDelayed(TriggerRunner.java:931)
	at org.apache.jsp.setup.batchJobRun_jsp._jspService(batchJobRun_jsp.java:216)
	at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
	at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:390)
	at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:334)
	at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at com.rb.util.web.NoCacheFilter.doFilter(NoCacheFilter.java:41)
	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
	at org.apache.coyote.ajp.AjpAprProcessor.process(AjpAprProcessor.java:188)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)
	at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2440)
	at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2429)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
	at java.lang.Thread.run(Unknown Source)