That explains it....
Not on a Pi, but... I just started using HDMI on my laptop after a work monitor upgrade. My wireless mouse started to behave oddly - juddering and stuttering. I swapped the mouse dongle to the other side of my laptop and it all works fine. The original side has the USB right next to the HDMI. It does seem that something is interfering with 2.4 and HDMI generally and having the ports all close together (as they are on a Pi) will make it obvious.
Biting the hand that feeds IT
