JAS installation problem...

We've upgraded one of our JAS servers from AIX 4.3.3 to AIX 5.2.
After encountering some problems using HTML, we decided to reinstall (using SP22J_W1_RS6000,
which was what we were previously using).
After the installer gathers all the information it needs, the progress bar appears briefly
and then vanishes, leaving a screen that just says "null" for
the error that occurred. The log file on the server says:

(Jan 11, 2005 12:59:04 PM), Setup.product.install, com.installshield.product.ser
vice.product.PureJavaProductServiceImpl$Installer, err, java.lang.NullPointerExc
eption
STACK_TRACE: 12
java.lang.NullPointerException
at com.installshield.product.SoftwareObjectUtils.updateKey(SoftwareObjec
tUtils.java:21)
at com.installshield.product.service.product.PureJavaProductServiceImpl$
InstallProduct.addToVPD(PureJavaProductServiceImpl.java:4676)
at com.installshield.product.service.product.PureJavaProductServiceImpl$
InstallProduct.checkInstalledVersion(PureJavaProductServiceImpl.java:4632)
at com.installshield.product.service.product.InstallableObjectVisitor.vi
sitSoftwareObject(InstallableObjectVisitor.java:252)
at com.installshield.product.service.product.InstallableObjectVisitor.vi
sitProductBean(InstallableObjectVisitor.java(Compiled Code))
at com.installshield.product.service.product.InstallableObjectVisitor.vi
sitProductBeans(InstallableObjectVisitor.java(Compiled Code))
at com.installshield.product.service.product.PureJavaProductServiceImpl$
InstallProduct.install(PureJavaProductServiceImpl.java:4355)
at com.installshield.product.service.product.PureJavaProductServiceImpl$
Installer.execute(PureJavaProductServiceImpl.java:3590)
at com.installshield.wizard.service.AsynchronousOperation.run(Asynchrono
usOperation.java:40)
at java.lang.Thread.run(Thread.java:513)

We're using WebSphere 4.0 Advanced Edition. We had been using Fixpack 5,
but we upgraded to 6 when we encountered the problem to see if that would
make a difference. We also applied a fix from IBM, PQ76047, when Fixpack 6
didn't fix the problem, but we still get the same results.

Help!!

Just wanted to follow up on this, in case anyone else has the same problem...
The installer for SP22_W1 doesn't work on AIX 5.2 -- we had to go to SP23_I1 on the JAS servers.