Arrrrggggghhhhh.
The issue turns out to be that the request for the developer package page on My Irex doesn't work in Safari. There's no error given, and you get returned to the main Welcome page, so there's no way to know it didn't work.
This
could be a Safari problem, but in my experience it usually only happens when a web designer has been lazy and not coded/tested his page for compatibility with anything other than IE.
Anyway, I've got Shell access now
Mark