I have a mac mini running OS 10.4 and an isight camera that I have repurposed to do nothing but serve as a camera source for icam. It is directly connected to an airport express which is a remote for the airport extreme router for the house. I find that I am able to connect to it from my iPad or iPhone from multiple locations both inside my network or on the road for 2-4 hours. Inevitably I get a no sources found and have to reboot the mini (no screen attached). I am using the latest icam source and client.
I am now reduced to having my mini automatically reboot once a day when I am away.
What gives?
Are you running 10.4 or 10.4.11 (the most up-to-date version of Tiger) ?
Is the mini a PPC or Intel?
If you are running Tiger on an old PPC mini with a FireWire iSight then the CPU usage is going to be quite high. For some reason FireWire webcams use much more CPU on those old minis than USB webcams in any application. I would try reducing the Motion Detection frequency to "Less Often" in the iCamSource or disabling it altogether to see if that helps with the mini's stability.
It would also help if you could see if the iCamSource is crashing or if it is the mini locking up or losing its network connection by either connecting a monitor or connecting to the mini via Remote Desktop or VNC to get more information about what the problem is.