WebSphere 6.1 - SSO Error

Hi,
We recently upgraded our WebSphere version from 6.0.1 to 6.1 on our iSeries.  We also upgraded Lawson from Apps 9.0.0.4 to 9.0.0.8 and LSF 9.0.0.3 to 9.0.0.9. On our test box, it ran fine.  We are running on an iSeries machine running V5R4 of the OS. 

On production, now I receive an error message "Portal cannot load because it cannot initialize the single sign-on component.' I've followed Lawson's suggestions (KB articles 5395756, 1000235, 5335439, 550535). There does seem to be a problem with the plug-in file (when I look at it in the environment section of WebSphere Integrated Solutions Console). The problem seems to resolve when I generate and propagate the plug in.  However, when Lawson is stopped and started again twice, the error recurs.  I generate and propagate the plug-in and it works for two stops and starts again.  Any ideas what could be causing Lawson and/or WebSphere to 'forget' the plug-in information? 

Any ideas would be appreciated.
Thanks!
Stephen