Hey Met... I use Google Chrome for browsing and am not having that problem. It's handy to know where you left off with the ongoing conversation and one of the things I like about Agora.

I know when I clear my browsing history and clear my cookies that everything will look the same (read or un-read). It could be that your browser settings are not allowing these cookies onto your PC or are ignoring the cookies. Just a hint as to where to start looking with your system...