I’m on the Order Page, I then clicked on Forums….
"Only secure content is displayed" ------ "Show all content" appears.
I click on "Show all content" , and now I’m on the Forum main page.
Now if I click on any of the topics....
"Only secure content is displayed" ------ "Show all content" appears again.
I click on "Show all content'' , and that Topic will appear, etc, etc…..
Like I said this happens ( at least so far it seems ) only if I start out on my "Order page".
AFAIK that warning is settable in the browser to warn when a secure (https) page loads some of its content (an image, script or something like that) insecurely (http) .
Skimming over the forum index html source when using https to access the forum:
the stylesheet link "http://www.rightstuf.com/rsstatic/animeToday/forums/forum-screen.css"
(see the http instead of https there) might be the cause of the warning.
Now that I think about it: the forum allows remote avatars, so http content in a https page is kind of unavoidable...

If you'd absolutely would want to have the forum not cause such "mixed content" warnings, I guess you'd have to completely force the forum to http or at most use https for login.
Oh and a remark to Rightstuf: it might not be optimal to broadcast to the world what your LAN IP range is

:
( input type="hidden" name="curl" value="http%3A%2F%2F192.168.4.29%2Fubbthreads%2Fubbthreads.php%2Fforum_summary.html )
Feel free to moderator-edit out these last few lines.