Bad Version Number in Class File

I deployed an updated Ant extension to my cluster this afternoon (Windows agents).  What I have seen is that when agents are running in console mode they are fine.  But if they are running as a service I see an infinite loop of exceptions like this.  Any idea why it's different depending on console vs. service mode?  The service logs in as the same user account that I run the console agent as.  I have also rebooted to ensure all system variables are consistent for both.

Thanks for any ideas.

Tom

[jar:file:/C:/BuildAgent/plugins/BCDevAntExtension/lib/BCDevAntExtension.jar!/META-INF/build-agent-plugin.xml]: problem with class file or dependent class; nested exception is java.lang.UnsupportedClassVersionError: Bad version number in .class file
INFO   | jvm 1    | 2009/02/13 16:29:13 |     at org.springframework.beans.factory.support.ConstructorResolver.createArgumentArray(ConstructorResolver.java:570)
INFO   | jvm 1    | 2009/02/13 16:29:13 |     at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:190)
INFO   | jvm 1    | 2009/02/13 16:29:13 |     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:923)
INFO   | jvm 1    | 2009/02/13 16:29:13 |     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:833)
INFO   | jvm 1    | 2009/02/13 16:29:13 |     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:440)
INFO   | jvm 1    | 2009/02/13 16:29:13 |     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory$1.run(AbstractAutowireCapableBeanFactory.java:409)
INFO   | jvm 1    | 2009/02/13 16:29:13 |     at java.security.AccessController.doPrivileged(Native Method)
INFO   | jvm 1    | 2009/02/13 16:29:13 |     at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:380)