It doesn't matter what browser you're using, but you may need to clear out the browser's cookies. The login on the home page was tied to both front page (joomla) and phpbb. Two different pieces of software running the site, joomla has a default automatic logout of 15 minutes of inactivity (I bumped it up to 25 minutes last night, and Mo still had problems). That login module may have been the cause of being bumped out, so I got rid of it for now. I always log into the forum and hardly use the log in on the homepage (if ever), and never get bumped. I can surf other sites for long period and still post without problems. But I wouldn't be surprised if there are still cookies in your browser from previous sessions that may be causing trouble...that's why I recommend clearing them.
For chrome...go to the wrench, "Preferences", "under the hood," from the drop down box select "the begining of time" and check "Delete cookies and other site plug-in data." I often set my browsers to delete cookies when I close them. It can be a little bit of a hassle in terms of remember passwords for sites and such. But I like my computer being "clean" as possible. And as mentioned above I don't have problems being logged out, so that may be the solution?
*Of course, our site's consistent server timeouts can cause problems as well.
"Sometimes things go wrong, even when you're doing your best. That just shows that none of us are perfect. So I keep trying with all of my heart, and if that's not good enough, I'm not going to hang my head." - Luis Tiant