Mine are:

Cookie domain - .terraqueous.f2o.org
Cookie name - phpBBDGDev
Cookie path - /
Cookie secure - Disabled
Session length [ seconds ] - 3600

I've read that the dot at the start of the domain is very important

Either that or:

leave domain blank or
no dot at the start, add dot at the end eg. terraqueous.f2o.org.

None of these have worked, I haven't tried www.terraqueous.f2o.org yet

It's a case of trial and error, I think