It may happen when you're using any other USB device on the SFPro? Such as the SD card, Wi-Fi, ...?I bought the Plugable UD-3900 and a mini Display Port to HDMI converter to power my two monitors on the SP2. I have been experiencing poor performance when doing something as simple as typing an email or searching for something online. Does anyone know if there is a reason for this? This slow performance doens't happen all the time either and I can't figure out why. On a previous post it warned of slower performace but I didn't think it would this bad. If anyone has any suggestions on how to fix it that would be great.