Firefox’ plugin hang detector is a feature that aims to reduce browser crashing caused by plugins like Flash or Silverlight hanging for prolonged periods of time. Firefox will cut a plugin process off after a predefined timeout, set to 15 seconds by default. While I loudly applaud this stability feature, it is an annoying one to deal with if you’re a Flash developer using a debugger. Setting breakpoints for longer than 15 seconds will trigger the hang detector and break off your debugging session. Very annoying indeed.
Fortunately, there is a way to disable this feature (or set the timout to something more usable).
Step 1: about:config
Open up a new tab and type about:config to bring up the advanced configuration page. Click past the warning ;-).
Step 2: Set timeout to -1 to disable
Use the filter field to search for dom.ipc.plugins.timeoutSecs and set its value to -1 to disable the detector entirely. Of course, you’re free to set it to any higher value, just remember that the timeout is expressed in seconds and you’re good to go.