It's an issue with cookies since they're in the process of changing the forums to https
If the URL starts with https you should be fine, if it starts with http it can be a bit weird and not save logins correctly (because I believe the cookies are configured to work on https? unsure tbh).
viewtopic.php?f=11&t=95524Addition by TurdPile: Forums have been toggled to prefer HTTPS. Users may experience weirdness trying to log into the forums if they are not using HTTPS. (https:// in the URL). This will persist until everything is done being forced to HTTPS. If you are having this issue, just add the s to "http" to the URL.