old chrome, audio problems with flash, mac

Not really.  It's hard to know why the echo is happening.  If one of you is using the chassis mic and speakers instead of a headset, that's a good indicator that the VOIP application isn't using the enhanced Audio APIs, which support Acoustic Echo Cancellation. The legacy audio APIs would definitely have echo if the mic is able to hear the speakers.  If it's some other kind of latency-related echo, then there's really not a lot you can do about it.  It depends on how they've implemented things.  There's a lot of freedom in AS3 to implement video conferencing in non-optimal ways.  It's definitely possible to do conferencing well with Flash, which suggests room for improvement in the content provider's implementation and/or infrastructure.