That's strange. Have you tried typing the IP address of the camera (the same one that you have entered in icamsource) into your Internet browser's address bar to see if it will connect?
If you are able to connect, you might try clearing your icamsource settings by following these directions for Windows:
Run this file and confirm that you want to import it into your registry:
http://skjm.com/icam/CleaniCamKey.regOr these directions for Mac:
To clear the settings on a Mac, follow the directions here to delete the plist file:
http://skjm.com/forum/index.php?topic=582.msg12900#msg12900Once you clear the settings, you'll have to re-add all of the cameras/settings as if you were starting from scratch.
If none of that helps, have you made sure that your camera has the latest firmware installed? It could be a weird firmware issue that's causing connection issues with the mjpeg feed.
Finally, you might consider not using any camera's built-in proxy service, as that sends your video feed through their servers...and who know if it's secure or not. Personally, I wouldn't trust any proxy that I didn't control or that didn't have major security/encryption built-in. IP camera hacks have been all over the news lately, and I believe most victims were found by using these free public proxies that are provided by the camera manufacturers.