This is not a top issue/bug, and in fact, im not sure this is about Plus.. maybe it is

I open 3 conversation windows and i can see on the tabs. I have active the third tab and go to IE to see something.. the status bar goes orange, wish means i have a new msg, but the msg is from the second tab but it shows the third nick.. as i say, is not a big deal but is a little confusing sometimes

See the screenshot

The taskbar allways show the active window, even tough there's a new msg from another user. When you open the convos you'll see at first the active convo. The one with new msgs will be blinking.

So, I guess there's no bug.