OK, I changed my settings:
cookie path was already set to / but the cookie domain was blank. I've changed this to be the domain name, i.e. test.example.com.
I've then changed the PP config settings. The forum cookie prefix was blank and I changed this to bb. My vB
license info was already defined. The cookie path was already / and I changed the cookie domain from being blank to test.example.com.
This certainly cures the problem with being logged onto vB
with one user and it actually being logged in as another within photopost, however now when the test user logs on, it still says he's unregistered (see attachment).