A quite large project that has been going on jdk 1.5 previously. Setting JDK to 1.6 and trying to run it. Each attempt results in "caches corrupt" message and full rebuild. Trying to run after the full rebuild - caches corrupt again, full rebuild again. What have I tried and it did not help: 1. Cleared IDEA caches in ~/.IntelliJIDEA6/system 2. Run rebuild all manually 3. Run rebuild and kept IDEA window on the front - i.e. no syncs The following exception has shown up during the process: java.lang.UnsupportedClassVersionError: Bad version number in .class file java.lang.RuntimeException: java.lang.UnsupportedClassVersionError: Bad version number in .class file at com.intellij.compiler.impl.CompileDriver.a(CompileDriver.java:642) at com.intellij.compiler.impl.CompileDriver.access$400(CompileDriver.java:609) at com.intellij.compiler.impl.CompileDriver$5$1.run(CompileDriver.java:5) at com.intellij.openapi.progress.impl.ProgressManagerImpl.runProcess(ProgressManagerImpl.java:38) at com.intellij.compiler.impl.CompileDriver$5.run(CompileDriver.java:3) Caused by: java.lang.UnsupportedClassVersionError: Bad version number in .class file at java.lang.ClassLoader.defineClass1(Native Method) at java.lang.ClassLoader.defineClass(ClassLoader.java:620) at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124) at java.net.URLClassLoader.defineClass(URLClassLoader.java:260) at java.net.URLClassLoader.access$100(URLClassLoader.java:56) at java.net.URLClassLoader$1.run(URLClassLoader.java:195) at java.security.AccessController.doPrivileged(Native Method) at java.net.URLClassLoader.findClass(URLClassLoader.java:188) at java.lang.ClassLoader.loadClass(ClassLoader.java:306) at java.lang.ClassLoader.loadClass(ClassLoader.java:251) at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Class.java:242) at com.intellij.uiDesigner.compiler.Utils.validateJComponentClass(Utils.java:138) at com.intellij.uiDesigner.lw.CompiledClassPropertiesProvider.getLwProperties(CompiledClassPropertiesProvider.java:49) at com.intellij.uiDesigner.lw.LwComponent.readProperties(LwComponent.java:219) at com.intellij.uiDesigner.lw.LwAtomicComponent.read(LwAtomicComponent.java:32) at com.intellij.uiDesigner.lw.LwContainer.readChildren(LwContainer.java:262) at com.intellij.uiDesigner.lw.LwContainer.read(LwContainer.java:367) at com.intellij.uiDesigner.lw.LwRootContainer.read(LwRootContainer.java:84) at com.intellij.uiDesigner.compiler.Utils.getRootContainer(Utils.java:72) at com.intellij.uiDesigner.make.Form2ByteCodeCompiler$2.run(Form2ByteCodeCompiler.java:3) at com.intellij.openapi.application.impl.ApplicationImpl.runReadAction(ApplicationImpl.java:308) at com.intellij.uiDesigner.make.Form2ByteCodeCompiler.process(Form2ByteCodeCompiler.java:15) at com.intellij.compiler.impl.FileProcessingCompilerAdapter.process(FileProcessingCompilerAdapter.java:5) at com.intellij.compiler.impl.FixedTimestampCompilerAdapter.process(FixedTimestampCompilerAdapter.java:14) at com.intellij.compiler.impl.CompileDriver.a(CompileDriver.java:59) at com.intellij.compiler.impl.CompileDriver.a(CompileDriver.java:288) at com.intellij.compiler.impl.CompileDriver.a(CompileDriver.java:578) at com.intellij.compiler.impl.CompileDriver.a(CompileDriver.java:626) ... 4 more