It's very odd that it logs you out when you're replying to a post UNLESS a) that post, for whatever reason, has taking you a rather long period of time to compose; or b) You have the forum open to the message you want to reply to for a long time before hitting the reply button.
I would suspect that just hitting reply does NOT update the site cookie. I would think that things like clicking on 'New Posts' or even browsing to the main screen would update the cookie (just guessing here - nothing more - I could be WAAAAYYY off - it may only update cookie upon login and New Posts).
Does your roomie or her bf ever browse TP at all? Would they have any reason to? If not, it may be okay for you to check it anyway. Worse thing that happens is that they access your account here and post bad things... I'm sure were that to happen TP'd help you out and delete such posts (unless they post nudie pics of you, then he'll sticky it - right TP???
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