Below is an example stack trace. It does not always fail, and it does not fail on the same project every time:

FAILURE: Build failed with an exception.

• Where:
  Build file 'C:\Users\Adam\Documents\gradle\gradle\subprojects\gradle-antlr\antlr.gradle'

• What went wrong:
  Execution failed for task ':antlr:ideaModule'.
  Cause: Could not resolve all dependencies for configuration 'detachedConfiguration2'.
  Cause: java.io.FileNotFoundException: C:\Users\Adam\.gradle\cache\resolved-org.gradle-antlr-0.9-20100725113412+1000.xml
  (The requested operation cannot be performed on a file with a user-mapped section open)

• Try:
  Run with -S option to get the full (very verbose) stacktrace.

• Exception is:
  org.gradle.api.tasks.LocationAwareTaskExecutionException: Build file 'C:\Users\Adam\Documents\gradle\gradle\subprojects\
  gradle-antlr\antlr.gradle'
  Execution failed for task ':antlr:ideaModule'.
  at org.gradle.api.internal.tasks.DefaultTaskExecuter.executeActions(DefaultTaskExecuter.java:63)
  at org.gradle.api.internal.tasks.DefaultTaskExecuter.execute(DefaultTaskExecuter.java:41)
  at org.gradle.api.internal.project.taskfactory.PostExecutionAnalysisTaskExecuter.execute(PostExecutionAnalysisTa
  skExecuter.java:32)
  at org.gradle.api.internal.project.taskfactory.ExecutionShortCircuitTaskExecuter.execute(ExecutionShortCircuitTa
  skExecuter.java:50)
  at org.gradle.api.internal.tasks.SkipTaskExecuter.doExecute(SkipTaskExecuter.java:57)
  at org.gradle.api.internal.tasks.SkipTaskExecuter.execute(SkipTaskExecuter.java:35)
  at org.gradle.api.internal.tasks.ExecuteAtMostOnceTaskExecuter.execute(ExecuteAtMostOnceTaskExecuter.java:32)
  at org.gradle.api.internal.AbstractTask.execute(AbstractTask.java:231)
  at org.gradle.execution.DefaultTaskGraphExecuter.executeTask(DefaultTaskGraphExecuter.java:167)
  at org.gradle.execution.DefaultTaskGraphExecuter.doExecute(DefaultTaskGraphExecuter.java:160)
  at org.gradle.execution.DefaultTaskGraphExecuter.execute(DefaultTaskGraphExecuter.java:78)
  at org.gradle.execution.TaskNameResolvingBuildExecuter.execute(TaskNameResolvingBuildExecuter.java:161)
  at org.gradle.execution.DelegatingBuildExecuter.execute(DelegatingBuildExecuter.java:54)
  at org.gradle.initialization.DefaultGradleLauncher.doBuildStages(DefaultGradleLauncher.java:153)
  at org.gradle.initialization.DefaultGradleLauncher.doBuild(DefaultGradleLauncher.java:107)
  at org.gradle.initialization.DefaultGradleLauncher.run(DefaultGradleLauncher.java:75)
  at org.gradle.launcher.Main.execute(Main.java:93)
  at org.gradle.launcher.Main.main(Main.java:42)
  at org.gradle.launcher.GradleMain.main(GradleMain.java:49)
  Caused by: org.gradle.api.artifacts.ResolveException: Could not resolve all dependencies for configuration 'detachedConf
  iguration2'.
  at org.gradle.api.internal.artifacts.ivyservice.ErrorHandlingIvyService.wrapException(ErrorHandlingIvyService.ja
  va:63)
  at org.gradle.api.internal.artifacts.ivyservice.ErrorHandlingIvyService.access$000(ErrorHandlingIvyService.java:
  28)
  at org.gradle.api.internal.artifacts.ivyservice.ErrorHandlingIvyService$BrokenResolvedConfiguration.rethrowFailu
  re(ErrorHandlingIvyService.java:127)
  at org.gradle.api.internal.artifacts.configurations.DefaultConfiguration$ConfigurationFileCollection.getFiles(De
  faultConfiguration.java:495)
  at org.gradle.api.internal.artifacts.configurations.DefaultConfiguration.getFiles(DefaultConfiguration.java:169)

at org.gradle.plugins.idea.IdeaModule.getFiles(IdeaModule.groovy:242)
at org.gradle.plugins.idea.IdeaModule.this$5$getFiles(IdeaModule.groovy)
at org.gradle.plugins.idea.IdeaModule$this$5$getFiles.callCurrent(Unknown Source)
at org.gradle.plugins.idea.IdeaModule.getModuleLibraries(IdeaModule.groovy:190)
at org.gradle.plugins.idea.IdeaModule$_getDependencies_closure5.doCall(IdeaModule.groovy:157)
at org.gradle.plugins.idea.IdeaModule.getDependencies(IdeaModule.groovy:156)
at org.gradle.plugins.idea.IdeaModule_Decorated.getDependencies(Unknown Source)
at org.gradle.plugins.idea.IdeaModule_Decorated$getDependencies.callCurrent(Unknown Source)
at org.gradle.plugins.idea.IdeaModule.updateXML(IdeaModule.groovy:126)
at org.gradle.api.internal.BeanDynamicObject.invokeMethod(BeanDynamicObject.java:158)
at org.gradle.api.internal.CompositeDynamicObject.invokeMethod(CompositeDynamicObject.java:93)
at org.gradle.plugins.idea.IdeaModule_Decorated.invokeMethod(Unknown Source)
at org.gradle.util.ReflectionUtil.invoke(ReflectionUtil.groovy:23)
at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$2.execute(AnnotationProcessingTas
kFactory.java:131)
at org.gradle.api.internal.project.taskfactory.AnnotationProcessingTaskFactory$2.execute(AnnotationProcessingTas
kFactory.java:129)
at org.gradle.api.internal.tasks.DefaultTaskExecuter.executeActions(DefaultTaskExecuter.java:55)
... 18 common frames omitted
Caused by: java.lang.RuntimeException: java.io.FileNotFoundException: C:\Users\Adam\.gradle\cache\resolved-org.gradle-an
tlr-0.9-20100725113412+1000.xml (The requested operation cannot be performed on a file with a user-mapped section open)
at org.gradle.api.internal.artifacts.ivyservice.DefaultIvyDependencyResolver.resolve(DefaultIvyDependencyResolve
r.java:58)
at org.gradle.api.internal.artifacts.ivyservice.SelfResolvingDependencyResolver.resolve(SelfResolvingDependencyR
esolver.java:43)
at org.gradle.api.internal.artifacts.ivyservice.DefaultIvyService.resolve(DefaultIvyService.java:136)
at org.gradle.api.internal.artifacts.ivyservice.ShortcircuitEmptyConfigsIvyService.resolve(ShortcircuitEmptyConf
igsIvyService.java:68)
at org.gradle.api.internal.artifacts.ivyservice.ErrorHandlingIvyService.resolve(ErrorHandlingIvyService.java:52)

at org.gradle.api.internal.artifacts.configurations.DefaultConfiguration.getResolvedConfiguration(DefaultConfigu
ration.java:199)
at org.gradle.api.internal.artifacts.configurations.DefaultConfiguration$ConfigurationFileCollection.getFiles(De
faultConfiguration.java:493)
... 35 common frames omitted
Caused by: java.io.FileNotFoundException: C:\Users\Adam\.gradle\cache\resolved-org.gradle-antlr-0.9-20100725113412+1000.
xml (The requested operation cannot be performed on a file with a user-mapped section open)
at org.apache.ivy.plugins.parser.xml.XmlModuleDescriptorWriter.write(XmlModuleDescriptorWriter.java:69)
at org.apache.ivy.plugins.parser.xml.XmlModuleDescriptorWriter.write(XmlModuleDescriptorWriter.java:61)
at org.apache.ivy.core.module.descriptor.DefaultModuleDescriptor.toIvyFile(DefaultModuleDescriptor.java:549)
at org.apache.ivy.core.resolve.ResolveEngine.resolve(ResolveEngine.java:248)
at org.apache.ivy.Ivy.resolve(Ivy.java:512)
at org.gradle.api.internal.artifacts.ivyservice.DefaultIvyDependencyResolver.resolve(DefaultIvyDependencyResolve
r.java:56)
... 41 common frames omitted

BUILD FAILED