[#5140] - iReport 4.0.1 not loading report

I intalled iReport 4.0.1 in Win XP yesterday. I opened a report, modified, compiled and then closed iReport. I did this for 3-4 times during the entire day to work on few reports. It did worked properly. But suddently, it stopped working when I opened iReport i think may be for 5th time. When I try to load the report, it gives the following error always.

Error loading the report template:
java.lang.IllegalStateException: Level number 3 is not recognized.

Then I unstalled and reinstalled again. The problem still persisted with the first try.

Then I installed in another machine Windows 7. The same exact sequel repeated in another machine also.

Can you guys please fix this ASAP as my office work is completely blocked.