On my tablet right now, Chrome on Android and experienced two logouts, logged back in and changed my pass, but I am feeling paranoid. Reasons why this happened?
I experience this every now and then when I'm browsing bitcointalk on my android phone. I'll log in and open a thread, click on reply, and it asks me to log in. If I go back it shows me as still being logged in. So I'll tap reply again and it prompts me to log in. I go back and tap logout and it gives me an error, but if I log in without going back it works fine.
I wouldn't worry about it too much personally.