Hi,

This usually happens if the ActiveSync plugin is not registered properly.  You can try one of the following and see whether it fixes the problem.

1. Restart AS or machine - to restart AS kill wcescomm.exe

(If the above didn't fix the problem try the following)
2. Uninstall AS and reinstall it again

(If problem still not solved try this)
3. Manually register the emulator and AS plugin. Execute the following commands on a cmd shell
   a. devicemulator.exe /register
   b. dvcemumanager.exe /register
   c. regsvr32 deviceemulatorproxy.dll
   d. regsvr32 serdmaasplugin.dll
   e. regsvr32 deviceemulatorbootstrap.dll

The .exe and .dll files could be found under "C:\Program Files\Microsoft Device Emulator\1.0" assuming VS is installed under C: drive. 

deviceemulatorbootstrap.dll could be found under "C:\Program Files\Microsoft Visual Studio 8\SmartDevices\Emulators\DeviceEmulator"

After performing the above steps, restart AS.

Thanks
Siva