Issue: Can't post comment on home page articles

Note: The admin is aware of this, but it occurred to me that I should've posted my issue here. Sorry about that!
Someone out there may be having this same problem, and someone else might also know the answer.

Long story short, I am unable to post comments on the homepage's articles. (I tried with Firefox 11 & the newest version of Opera). Strangely, I can vote other people's comments up, but I cannot comment. Even after I login to the forum, I see the below image on the homepage:



It's as if the homepage isn't recognizing me, even though it takes me straight to the forum -- logged in-- if I click the "Community" link. So, obviously, my details are registering, but they don't 'stick' on the homepage for some reason.

1. It doesn't matter if I login to the forum first or the homepage first.
2. It doesn't matter if I clear all cache & cookies between attempts.
3. It doesn't matter how many times I refresh the forum page or homepage, or how many times I re-enter my details on the homepage.
4. Logging in via safemode (which disables all add-ons) makes no difference.

Btw, when I look at any article on the homepage after logging in, under "Write comment" it says "You must be logged in to post a comment. Please register if you do not have an account yet."

Any and all suggestions are greatly appreciated.