Hudson: Builds of multi-module maven project fail, then immediately succeed again - maven

Question

I have a multi-module project where the top level project serves both as the parent of the individual modules and as the project that declares the modules. Only this top level project is configured in Hudson (including automatic SVN checkout). The simplified layout is as follows:
ProjectRoot\
|
+---kernel\
| |
| +---pom.xml [ArtifactId=MyProject_kernel parent=MyProject]
|
+---model_foo\
| |
| +---pom.xml [ArtifactId=MyProject_model_foo, parent=MyProject]
|
+---pom.xml [ArtifactId=MyProject, parent=none]
Also, model_foo has a dependency on kernel.
Now, Hudson automatically discovers the kernel and model_foo sub projects, and it usually manages to build everything just fine.
However, each time I make a breaking change, such as create a new class in kernel and use it inside model_foo, I get a failing build for model_foo, followed by one that succeeds. The mail notifications are titled
Build failed in Hudson: MyProject » MyProject Model Foo #1545
Hudson build is back to normal : MyProject » MyProject Model Foo #1546
Why is that? I suspect it might have to do with the fact that the MyProject pom.xml is both the multi-module project and the parent of its modules, but before changing that I would like to know whether it's actually going to help.
I use Hudson 2.1.0.
Update
This is the log of a failed build of the web module (equals model_foo in the diagram above). The build for the MyProject root project had the same build number, and succeeded.
I stripped out the actual compiler errors, which are exactly the same as if the newly introduced class was missing.
Started by upstream project "MyProject" build number 1545
Found mavenVersion 2.0.9 from file jar:file:/home/builder/opt/apache-maven-2.0.9/lib/maven-2.0.9-uber.jar!/META-INF/maven/org.apache.maven/maven-core/pom.properties
$ /home/builder/opt/jdk1.5.0_22//bin/java -Xmx1024m -Xms512m -cp /home/builder/var/hudson/plugins/maven-plugin/WEB-INF/lib/maven-agent-2.1.0.jar:/home/builder/opt/apache-maven-2.0.9/boot/classworlds-1.1.jar hudson.maven.agent.Main /home/builder/opt/apache-maven-2.0.9 /home/builder/opt/apache-tomcat-6.0.24/webapps/hudson/WEB-INF/lib/hudson-remoting-2.1.0.jar /home/builder/var/hudson/plugins/maven-plugin/WEB-INF/lib/maven-interceptor-2.1.0.jar 48555
<===[HUDSON REMOTING CAPACITY]===> channel started
Executing Maven: -N -B -f <http://ciserver:8080/hudson/job/MyProject/com.mycompany.myproject$web/ws/pom.xml> clean deploy -Dworkspace.path=/home/builder/var/hudson/jobs/MyProject/workspace/ -Droot.project.name=MyRoot -e
+ Error stacktraces are turned on.
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[INFO] Building MyProject
[INFO] task-segment: [clean, deploy]
[INFO] ------------------------------------------------------------------------
[INFO] [clean:clean]
[INFO] Deleting directory <http://ciserver:8080/hudson/job/MyProject/com.mycompany.myproject$web/ws/target>
[INFO] [resources:resources]
[INFO] Using default encoding to copy filtered resources.
[INFO] [compiler:compile]
[INFO] Compiling 945 source files to <http://ciserver:8080/hudson/job/MyProject/com.mycompany.myproject$web/ws/target/classes>
[HUDSON] Archiving <http://ciserver:8080/hudson/job/MyProject/com.mycompany.myproject$web/ws/pom.xml> to /home/builder/var/hudson/jobs/MyProject/modules/com.mycompany.myproject$web/builds/2011-09-27_13-32-33/archive/com.mycompany.myproject/web/1.1-SNAPSHOT/pom.xml
[INFO] ------------------------------------------------------------------------
[ERROR] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Compilation failure
{{{compiler failure here}}}
[INFO] ------------------------------------------------------------------------
[INFO] Trace
org.apache.maven.BuildFailureException: Compilation failure
at org.apache.maven.lifecycle.DefaultLifecycleExecutor.executeGoals(DefaultLifecycleExecutor.java:579)
{{{stacktrace omitted}}}
Caused by: org.apache.maven.plugin.CompilationFailureException: Compilation failure
at org.apache.maven.plugin.AbstractCompilerMojo.execute(AbstractCompilerMojo.java:516)
{{{stacktrace omitted}}}
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 1 minute 7 seconds
[INFO] Finished at: Tue Sep 27 13:33:42 CEST 2011 [INFO] Final Memory: 53M/508M
[INFO] ------------------------------------------------------------------------