Will make this straight. My PC got stuck and restarted it. Upon restarting my PC I decided to login again to YM since i was chatting before it got stuck. I was also surfing the net before it hangged and so I run my Firefox and have my previous sites visited restarted. One of the sites was Yahoo mail. Since I am using the Yahoo mail with chat enabled, my chat status at Yahoo mail immediately became available. After being signed out at YM due to Yahoo mail, i login again at YM and i noticed that i wasn't signed out at Yahoo mail.
Very rare though. Normally, when you are logged in at Yahoo mail chat and decided to login at YM, your Yahoo mail chat will be logged out or vice versa. Anyway, i have here the screenshot of my chat to myself using both YM and Yahoo mail chat.
Notice also that some of my contacts that are offline at YM are still on-line at my Yahoo mail. That's for now. Happy chatting..