Build: NetBeans IDE 7.2 (Build 201207171143)
VM: Java HotSpot(TM) 64-Bit Server VM, 20.8-b03-424, Java(TM) SE Runtime Environment, 1.6.0_33-b03-424-11M3720
OS: Mac OS X

User Comments:
GUEST: Checkstyle maven plugin gives this issue a lot.

GUEST: When I pushed the SQE's "Run Checkstyle" button on the maven project,
 java.util.ConcurrentModificationException is occured.

The pom.xml is here.
-----
    <reporting>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-checkstyle-plugin</artifactId>
                <version>2.6</version>
                <configuration>
                    <configLocation>src/checkstyle/my_sun_checks.xml</configLocation>
                 </configuration>
            </plugin>
        </plugins>
    </reporting>
-----

If the "configLocation" was "config/sun_checks.xml", the SQE works  perfectly.
("config/sun_checks.xml" represents that the checkstyle-plugin use build-in check rule in the checkstyle) 

But when the "configLocation" was the filepath, the SEQ works fail.

la3lma: Checkstyle.

GUEST: Executing Quality plugin to get checkstyle errors from a project

GUEST: Attempting to run checkstyle plugin.  This always happens after first run.

GUEST: run quality checkstyle

GUEST: running several code quality utilities simultaneously




Stacktrace: 
java.util.ConcurrentModificationException
   at java.util.AbstractList$Itr.checkForComodification(AbstractList.java:372)
   at java.util.AbstractList$Itr.next(AbstractList.java:343)
   at org.nbheaven.sqe.tools.checkstyle.codedefects.core.ui.result.BugTree.createRootTreeNode(BugTree.java:141)
   at org.nbheaven.sqe.tools.checkstyle.codedefects.core.ui.result.BugTree.access$500(BugTree.java:43)
   at org.nbheaven.sqe.tools.checkstyle.codedefects.core.ui.result.BugTree$1.run(BugTree.java:91)
   at org.openide.util.RequestProcessor$Task.run(RequestProcessor.java:1452)