I'm running XF 3.1.1 with the aperature driver on netbsd-current, with 
a Logitech PS/2 mouse.  This is on an ASUS SP3G motherboard, with the 
on-board PS/2 mouse connector set to interrupt 12.

When X comes up, the mouse pointer is in the middle of the screen (as 
usual).  As soon as I move the mouse, the pointer jumps to the upper 
right corner of the screen.  Other movements cause random menus to 
flash on and off, as if I was pressing buttons.

The same mouse works fine under Windows and Linux/XF86 3.1.

I have re-created /dev/pms0 using an up-to-date MAKEDEV, so I hope it's 
not that.  The only other thing I've seen that looks relevant is that 
when X starts up, it tells me that I have a PS/2 mouse running at 1200 
baud; I don't recall having seen a "baud rate" reported under Linux.

 - irving -