UnsupportedClassVersionError

I'm having a build failure while running Ant on a HP-UX machine. Here's the output. Everything works OK until Ant invokes the compiler. Clearly, somethign is out of synch, but I don't know where to start looking.

init:

[delete] Deleting directory /privdir/cttc999/cmWizardBuild/196251/build

[echo] Building Test Application (ecm-test.jar)

[mkdir] Created dir: /privdir/cttc999/cmWizardBuild/196251/build

[echo] os.name: HP-UX

manifest:

compile:

[javac] Compiling 1 source file to /privdir/cttc999/cmWizardBuild/196251/build

BUILD FAILED

java.lang.UnsupportedClassVersionError: com/sun/tools/javac/Main (Unsupported major.minor version 48.0)

[710 byte] By [Dick_Adamsa] at [2007-10-2 14:31:26]