The only time I've seen mouse problems causing system lockups or other
weird operation is when the mouse itself has been faulty ( e.g. cable
mouse with broken wires ) or being interfered with ( e.g. wireless
mouse with something transmitting nearby or between it and receiver,
or excessive electrical noise generating spurious signals - one very
memorable case was a PSU putting out a lot of noise on the 5V line
which caused some extremely strange symptoms, erratic and random
cursor movement plus spurious clicks opening up windows - was very
impressive to see in operation but the system was totally unusable ).

Have you tried a different mouse ? Wired if using wireless, USB if
using PS/2 or vice-versa.