Hi I have one production server with Ubuntu 12.04  openERP 6.1 working just fine. Then I created another system with Ubuntu 14.04 and same openERP version (copy paste from production). But the last one always produces an error when I try to generate report like :

Failed to invoke method execute in class com.nantic.jasperreports.JasperServer: Error evaluating expression : 
Source text : (new java.net.URLClassLoader(
([new java.net.URL("file://" + $P{SUBREPORT_DIR})]
).toArray(new java.net.URL[0]), getClass().getClassLoader()
)).loadClass("Stopwatch").newInstance().start()

Kindly help what is the meaning of above error?

Rgds
Hans