Screenshots in Recovery

Hi.
I would like to take Screenshots of the Recovery (CWM 6.0.2.7) running on my Galaxy S3. I installed the Android SDK, and taking screenshots works as long as the device runs normally. but as soon as i boot into recovery i can't take Screenshots anymore, even though my device is still recognized. But instead of "Offline" the monitor only shows three question marks next my devices name.
Has anyone a solution for this?

Thanks in advance,
loyonyart