I don't have an answer but I have what appears to be the same problem. Happens fairly consistently about once a day. I notice it in the morning. Sometimes I can fix the problem by opening iCamSource and clicking "stop" but usually that doesn't work. So then I have to fire up Terminal, find the running process and kill it that way. Then, upon relaunching iCamSource it will work fine for another day.
My setup is fairly vanilla. An older MacBookPro 15-inch (MacBookPro4,1 specifically) with 6 gigs RAM, OS X 10.9.2 and OS X Server 3.1.1. I have two cameras in use, a Logitech C310 and some el-cheapo $10 webcam from OfficeMax. Not a huge show-stopper but frustrating.