How can someone else use my nickname in my chat? Was I hacked?

It's unlikely that you have been hacked. Attackers may attempt to use a nick that appears to be yours by using similar characters. If someone is harassing you in Ustream chats please type !911 and Ustream Administrator will join the chat room to assist.

If someone is telling you that they have hacked your account, don't worry, it is incredibly unlikely. That is, however, so long as you have a strong account password for both your Ustream account and the email you used to sign up with Ustream. To play it safe reset your passwords using random combinations of letters and numbers and always use a unique password for each service.