Recently I encountered an error , while working on iReports ,
iReport it was not able to compile .jrxml file to generate .jasper file , whilst it used to show compile time.
Compiling to file... ./<filename>.jasper -> /usr/share/iReport/bin/<filename>.java
Errors compiling ./<filename>.jasper.
net.sf.jasperreports.engine.JRException: Error saving expressions class file : /usr/share/iReport/bin/<filename>_1267071292035_83340.java
Compilation running time: 80
Basically I found two way out this situation
1) Changing permission of usr/share/iReport/bin/ directory .
This can be done with CHMOD command
sudo chmod 777 usr/share/iReport/bin
2) change the directory where reports are compiled.