Q:

Android Emulator not seen in Device Chooser

I have a weird problem here.  When I start an Emulator, it starts up after sometime but it is not shown in the Android Device Chooser(some times it is shown).  Has anyone encountered this situation before?  
Here is a screen shot of the situation.  As you can see, one emulator is running on port 5554 (GingerBreadGoogleAPI), but the Device Chooser shows no emulator or device is connected.  The cmd ./adb devices does not list any device. 
I am running Linux 3 kernel on Kubuntu OS with 2GB RAM. 
One solution (which I do) is to simply start another emulator.  But I dont want a solution for the problem, instead I want to know why this is happening. 

A:

It is happening sometimes; I am also facing this issue. 
I am always trying kill-server & start-server
You can find  ADB  under  SDK_Folder/platform-tools
First do
./adb kill-server

then
./adb start-server

and check
./adb devices

