The exact problem we were having was a bit odd. There were five people on the conference. Some of us could understand all parties involved perfectly. But for two people in particular (John and Pat), everything kept cutting in and out. So they'd only get syllables here and there. Yet Chris and I heard everyone perfectly.

Skype is horribly optimized. It's a processing and bandwidth hog.

The exact problem we were having was a bit odd. There were five people on the conference. Some of us could understand all parties involved perfectly. But for two people in particular (John and Pat), everything kept cutting in and out. So they'd only get syllables here and there. Yet Chris and I heard everyone perfectly.

We switched to Vent since it has an outside host and push-to-talk. But we could try another always-on client and see if it works better. I agree with some other folks that there would be value in having voice chat running constantly.

UPDATE: Shortly after I published this post, several friends suggested that I was making this perhaps too basic with regard to Skype. In fact, several deep and long posts could easily be written about Skype's supernode architecture as it is quite fascinating.

The point I was trying to make was that for nodes behind NAT/firewalls to communicate with other nodes behind NAT/firewalls, there needs to be some node outside of firewalls - on the public Internet - that can broker the communication between the endpoints.

In the case of Skype, we typically refer generically to those public nodes as "supernodes". In fact, the nodes known as "supernodes" perform the somewhat limited functions of connecting nodes together, providing a distributed database and choosing appropriate nodes to act as "relay nodes" when necessary.

These "relay nodes" are, in turn, the ones that perform the actual relaying of calls, messages, packets when direct connection is not possible. It is possible that these relay nodes could be located behind a NAT/firewall as the supernodes are connected to them and using them essentially to offload processing. Skype provides more info (including how to specify that your systems not be used as supernodes) in the IT Administrator's Guide I link to in the resources below.

In the IETF world of SIP, this external connection function is performed by either STUN or TURN servers (and that, too, could take up several blog posts).