I created a multi-module project and committed to Subversion (to a repository with several projects). I checked out the project only from Subversion. When I compiled the project there was an error message flashing by, that I couldn't read (it was too quick) and no .class files had been generated. There was no other error message. I removed the .ipr and the .iws from the repository, and checked out a new copy into a new (empty) multi-module project. Now it worked. It seems that they, or their paths became corrupted. Had a look in the logs and found a couple of suspicious things. Don't know if they are helpful or not to you but here they are: 2007-05-02 15:52:40,590 [24982794] ERROR - plication.impl.ApplicationImpl - java.lang.RuntimeException: java.lang.NullPointerException at com.intellij.compiler.impl.CompileDriver.a(CompileDriver.java:579) at com.intellij.compiler.impl.CompileDriver.access$400(CompileDriver.java:493) at com.intellij.compiler.impl.CompileDriver$5$1.run(CompileDriver.java:4) at com.intellij.openapi.progress.impl.ProgressManagerImpl$2.run(ProgressManagerImpl.java:3) at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:51) at com.intellij.openapi.progress.impl.ProgressManagerImpl.runProcess(ProgressManagerImpl.java:43) at com.intellij.compiler.impl.CompileDriver$5.run(CompileDriver.java:2) at com.intellij.openapi.application.impl.ApplicationImpl$4.run(ApplicationImpl.java) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:417) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:269) at java.util.concurrent.FutureTask.run(FutureTask.java:123) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:650) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:675) at java.lang.Thread.run(Thread.java:595) at com.intellij.openapi.application.impl.ApplicationImpl$1$1.run(ApplicationImpl.java:8) and 2007-05-02 15:52:40,520 [24982724] ERROR - ompiler.BackendCompilerWrapper - Sources output dir is null for module "BindowsPackager" java.lang.Throwable at com.intellij.openapi.diagnostic.Logger.error(Logger.java:48) at com.intellij.compiler.impl.javaCompiler.BackendCompilerWrapper$5.run(BackendCompilerWrapper.java:4) at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:303) at com.intellij.compiler.impl.javaCompiler.BackendCompilerWrapper.a(BackendCompilerWrapper.java:107) at com.intellij.compiler.impl.javaCompiler.BackendCompilerWrapper.compile(BackendCompilerWrapper.java:114) at com.intellij.compiler.impl.javaCompiler.JavaCompiler.compile(JavaCompiler.java:11) at com.intellij.compiler.impl.CompileDriver.a(CompileDriver.java:483) at com.intellij.compiler.impl.CompileDriver.a(CompileDriver.java:561) at com.intellij.compiler.impl.CompileDriver.a(CompileDriver.java:245) at com.intellij.compiler.impl.CompileDriver.a(CompileDriver.java:259) at com.intellij.compiler.impl.CompileDriver.access$400(CompileDriver.java:493) at com.intellij.compiler.impl.CompileDriver$5$1.run(CompileDriver.java:4) at com.intellij.openapi.progress.impl.ProgressManagerImpl$2.run(ProgressManagerImpl.java:3) at com.intellij.openapi.progress.impl.ProgressManagerImpl.executeProcessUnderProgress(ProgressManagerImpl.java:51) at com.intellij.openapi.progress.impl.ProgressManagerImpl.runProcess(ProgressManagerImpl.java:43) at com.intellij.compiler.impl.CompileDriver$5.run(CompileDriver.java:2) at com.intellij.openapi.application.impl.ApplicationImpl$4.run(ApplicationImpl.java) at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:417) at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:269) at java.util.concurrent.FutureTask.run(FutureTask.java:123) at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:650) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:675) at java.lang.Thread.run(Thread.java:595) at com.intellij.openapi.application.impl.ApplicationImpl$1$1.run(ApplicationImpl.java:8)