Strange error while deploying application client

Yesterday my app client was working perfectly. I worked on a different computer though but today as I wanted to test my app client again I encountered this strange error:

Copying 1 file to G:\StressLabo\StressLabo-app-client\dist

run-tool:

23-feb-2007 12:51:44 com.sun.enterprise.appclient.MainWithModuleSupport <init>

WARNING: ACC003: Application threw an exception.

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 sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:268)

at java.lang.ClassLoader.loadClass(ClassLoader.java:299)

at java.lang.ClassLoader.loadClass(ClassLoader.java:251)

at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)

at java.lang.Class.getDeclaredFields0(Native Method)

at java.lang.Class.privateGetDeclaredFields(Class.java:2259)

at java.lang.Class.getDeclaredField(Class.java:1852)

at com.sun.enterprise.deployment.util.DefaultDOLVisitor.acceptWithCL(DefaultDOLVisitor.java:349)

at com.sun.enterprise.deployment.util.EjbBundleValidator.accept(EjbBundleValidator.java:196)

at com.sun.enterprise.deployment.ApplicationClientDescriptor.visit(ApplicationClientDescriptor.java:620)

at com.sun.enterprise.deployment.archivist.AppClientArchivist.validate(AppClientArchivist.java:148)

at com.sun.enterprise.appclient.AppClientInfo.completeInit(AppClientInfo.java:177)

at com.sun.enterprise.appclient.AppClientInfoFactory.buildAppClientInfo(AppClientInfoFactory.java:136)

at com.sun.enterprise.appclient.MainWithModuleSupport.<init>(MainWithModuleSupport.java:287)

at com.sun.enterprise.appclient.Main.main(Main.java:180)

Exception in thread"main" java.lang.RuntimeException: java.lang.UnsupportedClassVersionError: Bad version number in .class file

at com.sun.enterprise.appclient.MainWithModuleSupport.<init>(MainWithModuleSupport.java:364)