Trackpad cursor gets jumpy with external projector...

I have a circa 2010 MacBook. I have been using it for 3 years with various problems here and there, but I just can't figure this one out.

I am a teacher, and I moved to a new classroom this year. The room has an overhead projector, Epson, and I hook it up to my mac through the minidisplay adapter (same style as Thunderbolt).

I have been using external monitors and projectors with this machine and they have worked fine. But with this projector on this day, every time I plug in and turn it on, the cursor gets all buggy and starts flying all over the place. If I plug in with the projector off, it's fine. If I plug into my external monitor, it works fine. It's just this particular projector in this room.

I have restarted the computer, and I still have this problem. Not sure what else to do. It's not a trackpad issue... it's only with this projector. Thanks!