Forum issues

hi
I am running the latest drupal release and I am experiencing the following problem in my forum:
I can post a new discussion, but I am not able to reply to any discussion, even as superadministrator. Any hint?

When I try to post a new discusion, I see both save and preview buttons, and they both work.
When I try to reply, I see only the preview button, and it doesn't work since even if i push it, th page remains the same and I am only able to "preview" (but it seems that the preview doesn't really wok). I've checked my administration, and the "preview" is just optional, user aren't forced to preview their contents before posting.

Thank you