Hi,
Looking at ProcessFakeTouches in UICamera.cs, we had to make one small change for the mouse to work.
In the if statement, when it sets the current touch to mMouse[0], it currently sets the currentTouchID to 1.
Looking at the comments at the top of the file, the touch ID to use for the left mouse button is -1.
We changed the line from:
to
and things started working as expected.
If this fix is correct, could it be rolled in the next version of NGUI?
Hope this helps somebody else

Thanks!