Just to add: I just inspected /usr/ibm/common/acsi/logs/root/acu_de.log and
found this error:

11-05-2012 14:04:04.122Exec returned stderr: JVMJ9CL005E Incompatible class
library version: requires VM v11, found v8
JVMJ9VM015W Initialization error for library jclscar_24(14): JVMJ9VM009E
J9VMDllMain failed
Could not create the Java virtual machine.

11-05-2012 14:04:04.200Code Page:  null
11-05-2012 14:04:04.201Code Page:  null
11-05-2012 14:04:04.203Waiting for exec to finish...
11-05-2012 14:04:04.987Exec returned exit value: 0
11-05-2012 14:04:04.988Waiting for stdout reading thread to die...
11-05-2012 14:04:04.989Exec returned stdout:
11-05-2012 14:04:04.989Waiting for stderr reading thread to die...
11-05-2012 14:04:04.990Exec returned stderr: java version "1.6.0"
Java(TM) SE Runtime Environment (build pap6460sr9fp1-20110208_03(SR9 FP1))
IBM J9 VM (build 2.4, JRE 1.6.0 IBM J9 2.4 AIX ppc64-64
jvmap6460sr9-20110203_74623 (JIT enabled, AOT enabled)
J9VM - 20110203_074623
JIT  - r9_20101028_17488ifx3
GC   - 20101027_AA)
JCL  - 20110203_01

Also /usr/ibm/common/acsi/logs/root/DE_Install.log contained this error:

        lax.nl.message.vm.not.loaded = The installer either could not find
a Java VM, or the Java VM on this system is too old. The installer requires
Java 1.1.5 or later. It can be download
ed from http://java.sun.com/products/jdk/1.1/jre/
        lax.resource.dir = AIX
        lax.stderr.redirect = /stderr
        lax.stdout.redirect = /stdout
        lax.user.dir = /tmp/install.dir.2425148
        lax.version = 11.5
        line.separator =

        os.arch = ppc64
        os.encoding = ISO8859-1
        os.name = AIX
        os.type = AIX
        os.version = 7.1
        path.separator = :
        si_java_home = /tmp/install.dir.2425148/AIX/resource/jre/jre
        sun.arch.data.model = 64
@

I just had a default AIX 7.1 TL1 SP1 installation without any special
additions.

Richard.