Mouse Pointer Size Increase Problem

i have got some problem on the mouse pointer, after start the windows, and run few minutes, the size of the pointer just changed bigger itself, i haven't do anything, just use my PC as normal (e.g. after restart just open firefox and get onto internet), but few minutes later it just become bigger, i have try to go to system to set the Scheme but it just stay the same. can anyone help?

p.s. i'm not sure about this, but seems this happened when i use firefox when i scroll up and down on it, it was fine yesterday, but today i had few changing on my PC, first is i have change my display card from 2600 pro to 5700, second is firefox updated to 3.5.5, i'm not sure whether those effect anything.

p.p.s. my mouse is logitech MX1000 on ps2 port, with installed logitech setpoint 4.80, here are some picture for reference, hope someone can help my with this issue, i just want it to be small.., thanks alot~

more information, after the mouse pointer size increased, when i hold the left click on the top bar of the open box to move it, the size of the pointer will back to normal (just when i hold it to move something), but when i release the mouse, the size of the pointer will change back to bigger....-____-""