Have a look at the timestamp on your jsp. It is
probably "in the future" compared to your machine.
That is what it was, my build machine time was 1 hour ahead of the JBoss server machine.
I experienced the same but fro a diffeent - as yet unknown - reason.
I'm running jboss 2.4.4 + tomcat 4.0.1.
I redeployed an app I'd just built on the same machine with ant. The build process involves copying the jsp (and others) out of a skeleton into the app structure then creating jar and ear.
The mod time for the jsp was 13:47:24 on disk and in the jar file. In the deployed form the jsp had the time 16:47:24, 3 hours later.
I haven't figured out why it happens - looks like the unjarring is having problems, but my problems and other might be solved by setting the mod-time to that of the deployment rather than the build.