1. Does it happen with all the applications?
2. What is the type of mouse you are using? Is it wired or wireless?
3. Is it a laptop or desktop computer?
4. What is the make and model number of the mouse?
I would suggest that you check if the mouse settings are correct.
1. OpenMouse by clicking theStart button, clickingControl Panel, clickingHardware, and then clickingMouse.
2. Click the Pointer Options tab, and then do any of the following:
If it works fine in safe mode, then try performing clean boot and check if it helps, here is the link:
You can start Windows 7 by using a minimal set of drivers and startup programs. This kind of startup is known as a "clean boot." A clean boot helps eliminate software conflicts. This article describes how to troubleshoot problems in Windows 7 by performing
a clean boot. http://support.microsoft.com/kb/929135
Make sure that you put back the computer to normal startup mode once it is done.
If you are using touchpad, try reducing the Touch Pad sensitivity and check if it helps.