I used to have this problem a lot, and related ones, but ever since I've started logging out and back in each time I use a new browser, I've not seen it. (That is, read BBS at work, go home, open browser, log out, log in, read BBS, go back to work, open browser, log out, log in, read BBS. But read BBS at work, go home, don't/ read BBS, go back to work, open browser, read BBS.)