people keep poping in and out and cannot hear each other.

Just as it says. two of the players keep popping in and out and cannot be heard. 

in and out of.......?

So you had two of your players appear in your game board but there was no sound from them, correct? Was this on the roll20 site or google hangout? What browsers were being used by everyone?  I know that a dev or a mod will probably be posting soon and will need more info but that should be a bare start of information they will need.

Brian, I could use some additional details although I am guessing you are referring to Audio/Video.  - Gauss

Was this with using Flash video? iTabletop uses Flash and has the same problem and we never managed to nail what causes it. With two people it always seems fine. Add a third or more, and on occasion, perhaps with some combination of browsers, you get one player unable to be heard by the others.

It was on this site, in a game session. A friend and I were using chrome and win 7 not certain of the others. One guy in particualer would pop in and out and when he came back had several camera icons going at once. At one point he had 5 of them. In the end we went to google hangout and accessed the site from there and had no problems. This site can get real buggy at times and has quirks to it like the initiative order. If you go from one map to another you must close the old order and make a new one.  

I'm assuming that you are using tokbox or the webrtc on the site board. Did the player or you have skype on? I've noticed that when skype is active and you are using tokbox (not sure about webrtc), there are glitches. My group discovered that the hard way during our first two sessions. Our work around is to disable the on site voice/video and use skype but others disable/close/shutdown skype and use tokbox/webrtc. Also make sure everyone is using the most up to date browser, that helps somewhat also. I think one of the browsers needs to be one version short of the latest but I'm not sure about which if it is actually that way now.

Brian,  Tokbox is a 3rd party program and not something we have a lot of control over. Many people are using google+ hangouts instead.  Regarding the Turn Order (initative order), it is a known issue that you need to close the Turn Order for a new map. Thank you for reporting this.  You mentioned the site getting buggy. Could you supply details? The more specific the better. - Gauss