Seems violations is looking up the slave (unix) file path within the master's (windows) file system.
With violations disabled, the build finishes without issue.

[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 55 seconds
[INFO] Finished at: Mon Feb 01 11:39:20 EST 2010
[INFO] Final Memory: 41M/306M
[INFO] ------------------------------------------------------------------------
ERROR: Processing failed due to a bug in the code. Please report this to users@hudson.dev.java.net
C:\data\itdev\hudson\workspace\XXXX JAR - SVN - Maven - UAT4\XXXX-Jar not found.
at org.apache.tools.ant.types.AbstractFileSet.getDirectoryScanner(AbstractFileSet.java:422)
at hudson.plugins.violations.ViolationsCollector.findFiles(ViolationsCollector.java:215)
at hudson.plugins.violations.ViolationsCollector.doType(ViolationsCollector.java:166)
at hudson.plugins.violations.ViolationsCollector.invoke(ViolationsCollector.java:110)
at hudson.plugins.violations.ViolationsCollector.invoke(ViolationsCollector.java:27)
at hudson.FilePath.act(FilePath.java:694)
at hudson.FilePath.act(FilePath.java:676)
at hudson.plugins.violations.hudson.maven.ViolationsMavenReporter.end(ViolationsMavenReporter.java:96)
at hudson.maven.MavenModuleSetBuild$Builder.end(MavenModuleSetBuild.java:678)
at hudson.maven.MavenModuleSetBuild$RunnerImpl.doRun(MavenModuleSetBuild.java:482)
at hudson.model.AbstractBuild$AbstractRunner.run(AbstractBuild.java:416)
at hudson.model.Run.run(Run.java:1198)
at hudson.maven.MavenModuleSetBuild.run(MavenModuleSetBuild.java:304)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:122)
project=hudson.maven.MavenModuleSet@16ce64e[XXXX JAR - SVN - Maven - UAT4]
project.getModules()=[hudson.maven.MavenModule@e72f0c[XXXX JAR - SVN - Maven - UAT4/com.xxxx:xxxx]]
project.getRootModule()=hudson.maven.MavenModule@e72f0c[XXXX JAR - SVN - Maven - UAT4/com.xxxx:xxxx]
FATAL: C:\data\itdev\hudson\workspace\XXXX JAR - SVN - Maven - UAT4\XXXX-Jar not found.
C:\data\itdev\hudson\workspace\XXXX JAR - SVN - Maven - UAT4\XXXX-Jar not found.
at org.apache.tools.ant.types.AbstractFileSet.getDirectoryScanner(AbstractFileSet.java:422)
at hudson.plugins.violations.ViolationsCollector.findFiles(ViolationsCollector.java:215)
at hudson.plugins.violations.ViolationsCollector.doType(ViolationsCollector.java:166)
at hudson.plugins.violations.ViolationsCollector.invoke(ViolationsCollector.java:110)
at hudson.plugins.violations.ViolationsCollector.invoke(ViolationsCollector.java:27)
at hudson.FilePath.act(FilePath.java:694)
at hudson.FilePath.act(FilePath.java:676)
at hudson.plugins.violations.hudson.maven.ViolationsMavenReporter.end(ViolationsMavenReporter.java:96)
at hudson.maven.MavenModuleSetBuild$Builder.end(MavenModuleSetBuild.java:678)
at hudson.maven.MavenModuleSetBuild$RunnerImpl.doRun(MavenModuleSetBuild.java:482)
at hudson.model.AbstractBuild$AbstractRunner.run(AbstractBuild.java:416)
at hudson.model.Run.run(Run.java:1198)
at hudson.maven.MavenModuleSetBuild.run(MavenModuleSetBuild.java:304)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:122)