What is your recording setup? I've had similar issues with using Ubercaster on the Mac, but it was the software routing of the audio that was the solution. Once I changed that, it corrected itself with using Skype. That was after eliminating all the hardware connections on the "studio" end, making sure everything was running out of my computer, through my mixer, and back into the computer without errors.
I usually run through the check list of things. Make sure that your headphones are not too loud that they are giving you slap back into your mic, but on The Crazy Canucks, we have two people in studio and up to three linked up on Skype. There's more things to consider in a situation like that.