iirc, I think gpm can also be configured to allow pasting between X and CLI on top of the usual feature of being able to copy and paste between virtual consoles. So in everyone's defense, it's good that they asked about gpm since it probably possible for it to play a part in a conflict or contention over the mouse.
I believe that some older versions of gpm used to cause such a conflict iirc. I do believe it was fixed by certain a version though. But still, it's usually best not to rule out such possibilities altogether when troubleshooting, because you just really never know for sure.
Also, I've had times when troubleshooting various things, that old bugs have crept back into new code as features were added (I'm sure everyone can relate to that sort of frustration at one time or another
I don't really use gpm much, but I know I've read somewhere about the above before. Either way, it's one of those things that good to know about since it could possibly save someone from a hair pulling experience that can happen very easily sometimes with Linux.