If a file in the workspace is a symlink whose target path isn't retrievable (say its absolute and isn't completely contained (relatively) in the workspace, then the task scanner plugin dies.

[TASKS] Scanning workspace files for tasks...
ERROR: Publisher hudson.plugins.tasks.TasksPublisher aborted due to exception
java.io.FileNotFoundException: "symlink source" (No such file or directory)
at java.io.FileInputStream.open(Native Method)
at java.io.FileInputStream.<init>(FileInputStream.java:137)
at hudson.FilePath.read(FilePath.java:1250)
at hudson.plugins.tasks.parser.WorkspaceScanner.invoke(WorkspaceScanner.java:140)
at hudson.plugins.tasks.parser.WorkspaceScanner.invoke(WorkspaceScanner.java:26)
at hudson.FilePath.act(FilePath.java:758)
at hudson.FilePath.act(FilePath.java:740)
at hudson.plugins.tasks.TasksPublisher.perform(TasksPublisher.java:206)
at hudson.plugins.analysis.core.HealthAwarePublisher.perform(HealthAwarePublisher.java:310)
at hudson.tasks.BuildStepMonitor$2.perform(BuildStepMonitor.java:27)
at hudson.model.AbstractBuild$AbstractRunner.perform(AbstractBuild.java:682)
at hudson.model.AbstractBuild$AbstractRunner.performAllBuildSteps(AbstractBuild.java:657)
at hudson.model.AbstractBuild$AbstractRunner.performAllBuildSteps(AbstractBuild.java:635)
at hudson.model.Build$RunnerImpl.post2(Build.java:161)
at hudson.model.AbstractBuild$AbstractRunner.post(AbstractBuild.java:604)
at hudson.model.Run.run(Run.java:1400)
at hudson.model.FreeStyleBuild.run(FreeStyleBuild.java:46)
at hudson.model.ResourceController.execute(ResourceController.java:88)
at hudson.model.Executor.run(Executor.java:175)
[ClearCase] Restored the original build steps.
Finished: FAILURE

Suggest Tasks Plugin just log something non fatal to console and continue in such circumstances.