There is one other thing that may cause the cursor (mouse pointer) to jump to a particular button by default.
Under Mouse Settings, there is an option called "Snap-To". This causes the mouse pointer to jump to the OK button by default.
On the Pointer Options tab, check/uncheck the box for "Snap To" - "Automatically move pointer to the default button in a dialogue box"
Sounds like what you describe. That option is in your standard mouse options. It could be called something different, depending on the model/make of mouse, but other than that it seems to be a standard Windows feature/option.
Andrew M