This is a very specific situation, where the application crashes only when run on an IBM Blade.
It runs fine on a local PC (Thats also a Quad core like the Blade) and runs fine on multiple VM servers that are hosted on an iSeries.
The Crash happens exactly at the end of the background worker process, after the processing is finished, that contains the web service.
Intrestingly enough, Try ... Catch blocks did not catch this.
To fix this I changed it over to a single threaded mode, however I left the all the Worker Thread code in there as comments.