Emma report generation failing with java.io.UTFDataFormatException: malformed input around byte 145

I am getting UTFDataFormatException while generating emma coverage report from coverage.ec and coverage.em.

I have instrumented the classes with emma maven plugin,
           <plugin>
                    <groupId>org.codehaus.mojo</groupId>
                        <artifactId>emma-maven-plugin</artifactId>
                        <inherited>true</inherited>   
                        <executions>
                            <execution>
                                <id>instrument</id>
                                <phase>process-test-classes</phase>
                                <goals>
                                    <goal>instrument</goal>
                                </goals>
                            </execution>                            
                        </executions>
                </plugin>

jdk version : ibm jdk 1.6
emma version : 2.0.5312
Deployed the Instrumented classes in tomcat to get the runtime coverage report.

Used the following command to generate the coverage report.
java emma report -r txt,xml -in coverage.ec,coverage.em

O/P : java.io.UTFDataFormatException: malformed input around byte 145
        at java.io.DataInputStream.readUTF(DataInputStream.java:650)
        at java.io.DataInputStream.readUTF(DataInputStream.java:558)
        at com.vladium.emma.data.MetaData.readExternal(MetaData.java:227)
        at com.vladium.emma.data.DataFactory.readEntry(DataFactory.java:770)
        at com.vladium.emma.data.DataFactory.mergeload(DataFactory.java:461)
        at com.vladium.emma.data.DataFactory.load(DataFactory.java:56)
        at com.vladium.emma.report.ReportProcessor._run(ReportProcessor.java:175)
        at com.vladium.emma.Processor.run(Processor.java:54)
        at com.vladium.emma.report.reportCommand.run(reportCommand.java:130)

Seems like coverage.em is causing this exception.

Is there any way to resolve this exception?