My mouse cursor wanders to the upper left hand corner of the screen by itself when my character is outside. This is really annoying and ONLY happens when my character is outside. This problem also seems to be limited to STARDEW VALLEY ONLY.

I am playing Stardew Valley on my Windows 7 Pro 64 PC. All my hardware drivers are up to date. I am using a expert XTracGear mouse pad that is the perfect mouse surface. My mouse is a laser mouse and has perfect tracking on everything else except for the aforementioned scenario.

What I've done/tried thus far to no avail;

Moved my WIRED mouse to another USB 2.0 port located directly from the main board on the back of my PC.
Checked my mouse surface for any debris, cleaned and tried again.
Cleaned my mouse sensor area.
Made sure no electrical interference was occurring via fluorescent light fixtures etc. etc.
Tried my mouse in several other games.

I dont know what else to try here to get my mouse cursor from automatically traveling to the upper left hand corner of my screen.

SORTED!!!!!!!!!

I have an XBox 360 wired USB controller that I use to play some games. It was plugged in at the same time. Apparently this game wont support a mouse + a game controller plugged in to the same PC at the same time.