Try a different mouse if you have one handy and see if problem persists.
If you use a wireless mouse make sure the batteries up fresh, when my batteries are going down I can get some crazy things going on with a mouse click
SeaSonic M12II 620W, ASUS M4A87TD EVO AM3 AMD 870, AMD Phenom II X4 925 Deneb 2.8GHz, Crucial 8GB (4 x 2GB) DDR3 1333, SAPPHIRE Radeon HD 6850, Kingston HyperX 120G 120GB Solid State Boot Drive, WD Caviar 1 TB Storage Drive, LG DVD-RW, Samsung SyncMaster 226bw 21" LCD, Windows 7 Home Premium 64bit