There is a new echo cancellation in RVC 5 that may be the change but as I remember the posts from last year that was only a one-line addition to the source. Should not cause any problems. I am not familiar with that source any more but if you have problems with RVC, I would recommend to switch to the more advanced SVC-SR Video Chat. If you paid for RVC and you don't have SVC-SR, give them an e-mail, they usually help you out.