phpbb <=> coppermine login

[Bismuth]

I seem to have the same problem as some people but none of the answers here seem to apply as far as I can see.

I installed Coppermine as downloaded and unmodified.
I ran the bridge manager and specified the bridge for 'phpbb 2.0.18 or later'

I try to log in in the gallery and I get sent to the forum login, OK so far.
I type in the username and password, submit, and get sent back to the gallery, but I'm still not logged in.
If I click 'Login' again, phpbb assures me I am logged in.

Coppermine install: http://www.southamptonrats.org/gallery/
Forum install: http://www.southamptonrats.org/phpbb2/
Coppermine version: cpg1.4.12
Forum version: phpBB 2.0.22
Test user account: test/test

Bridge database settings.
Short name: phpbb2018
Forum URL:  http://www.southamptonrats.org/phpbb2
Relative path to your BBS's config file:  ../../
Use post-based groups?:  0
Cookie name/prefix: soton_rats_forum

I'm afraid I'm at a loss of what to try next.
Any clues?

[Bismuth]

Should I manually set the coppermine config cookie name and path to be the same as phpbb's?

[Bismuth]

No, that didn't work either 

[Nibbler]

PHPBB cookie path has to be '/'. Read the manual.