Echo in Narration

Hi...I am recording narration the way I always have, but all of a sudden I am getting an echo in my narration.

I typically have the 'mute audio while recording' box checked, but out of curiosity tried it both ways today and get the very same echo.

I am using a clip microphone, which I have used successfully for the past 6 months.

I can't figure out what I might have done to cause the echo...any suggestions on where to start looking?

Thanks in Advance.

Lynn

ps...if  could figure out how to attach the audio clip, I will.