As already posted the problem with me is with 10.5.8 (not with 10.6.x).
In case it may be of interest for somebody, I tracked the cookies behaviour on my 10.5.8: a. without and b. with the problem. See below
Piero
a. When everything works:
a1. at Safari Start:
discussions.apple.com jive.recentHistory.252071 / ....
a2. click on: Support/Communities - or got here from e-mail
discussions.apple.com jive.server.info / "serverName=..."
discussions.apple.com BIGipServerPool_228 / ....
discussions.apple.com jive.recentHistory.252071 / ....
discussions.apple.com JSESSIONID / ....
a3. click Sign In and (user/password): Sign In
discussions.apple.com jive.server.info / "serverName=..."
discussions.apple.com BIGipServerPool_228 / ....
discussions.apple.com jive.recentHistory.252071 / ....
discussions.apple.com JSESSIONID / ....
discussions.apple.com ACEGI_SECURITY_HASHED_REMEMBER_ME_COOKIE / ....
discussions.apple.com jive.user.loggedIn / true
b. When it does NOT work:
b1. got here from e-mail
discussions.apple.com jive.server.info / "serverName=..."
discussions.apple.com BIGipServerPool_228 / ....
discussions.apple.com jive.recentHistory.-1 / ....
discussions.apple.com JSESSIONID / ....
discussions.apple.com myacinfo / INVALID
b2. click Sign In and (user/password): Sign In
Cookies: same as above
"We're sorry.
We're having a problem processing your login
9: invalid cookie supplied Unknown status code: 9
Return to Apple Support Communities."
b3. removed INVALID cookie
b4. click on Apple Support Communities (on the same error page)
b5. everything works again ok
discussions.apple.com jive.server.info / "serverName=..."
discussions.apple.com BIGipServerPool_228 / ....
discussions.apple.com jive.recentHistory.-1 / ....
discussions.apple.com JSESSIONID / ....
discussions.apple.com ACEGI_SECURITY_HASHED_REMEMBER_ME_COOKIE / ....
discussions.apple.com jive.user.loggedIn / true