Customers will occasionally report an error similar to this when running a layer 2 scan.
"Could not start extension."
"The InterMapper Server cannot connect to the desired extension at 127.0.0.1:8185. The extension service is not responding."
This can be resolved by the following.
Please delete InterMapper_Settings/Extensions/com.dartware.switches/switches.pid file and relaunch intermapperd.
If that does not help you will need to reboot the system.
Note: Intermapper Settings can be found here per OS.