I did that, and with no mods/changed settings, everything worked fine. I changed settings/mods when I was at 1200x700, and did the following: All sound off, Drag on Geoscape with left mouse, show funds on UI, Drag edge scroll on Battlescape with left mouse, set scroll speed to four pips from zero, show arrows and TUs on path, Death Notifications On, Allow Building Queue, Start Psi training Any Time, Field Sromotions, Inventory Stats, Enhanced Soldier Sprites, Smooth Bullet Camera, Confirm Weapon Fire, Psi-capture, Psi-strength Development, Override Line of Fire, Aliens Pick Up Weapons, Craft Carry Capacity, Gun Melee, Starting Missles, Fighter Transports, Pistol Auto-fire, Skyranger Weapon Slot, Improved Starting Base, Improved Starting Base Defense, and Statstrings. At 640x400 with these settings, it worked normally. With 800x600, the selected space when clicking would be one south from the shown highlighted position. At 1200x700, the cursor was very specific. It would only select the highlighted space if the left box created by the highlight shape was clicked.