Shot in the twilight: is this in addition to a laptop pointing device?

Try adding a separate stanza specifically for the external mouse and use /dev/input/mouse1 (point the main mouse to mouse0).

I've got that mouse and I don't have that problem, so, for what it's worth:

input: USB HID v1.10 Mouse [Microsoft Microsoft 5-Button Mouse with IntelliEye(TM)] on usb1:2.0

Section "InputDevice"
        Identifier  "Mouse0"
        Driver      "mouse"
        Option      "Device" "/dev/input/mice"
        Option      "Protocol" "ExplorerPS/2"
        Option      "Buttons" "7"
        Option      "ZAxisMapping" "6 7"
EndSection

Linux 2.4.22-1.2174.nptl (from Fedora)

I'd have a hard time believing the kernel is the difference, though, unless it was making itself obvious elsewhere, like dmesg.

I have no idea how I survived until now without thumb buttons. I now find myself pawing the sides of normal mice to no avail.

hmm, 2.6 did have that ps2 sensitivity screwup. Before you upgrade, put this in your lilo.conf:

append="psmouse_rate=60 psmouse_resolution=200"

heh- i secretly think that was for the early reviewers- going from 2.4.x to 2.6.x and the mouse moves a little faster translates to "it just *feels* faster" hahah-

Heh, no, I was actually bitten by it, the mouse going completely berzerker on me and killing windows in X when I accidentally touched it and stuff.

The external USB mouse was fine -- the braekage was only in the ps2 trackpoint (this is a laptop).

Weird- I had the same setup for a while and things worked perfectly (though I had 2 seperate input device sections, with USB sending events to the other one)- I guess it didnt affect setups like that.

the popular problem is you have two mouse entries in your stock xf86config. 2.6 added emulation so both devices provide data in duplicate.

Are you using a KVM switch? If so, have you tried plugging the mouse directly into the computer to see if you get the same results?

I've always had minor problems using the Intellimouse Explorer with my KVM switch, but I've found that switching to kernel 2.6 has made the problems worse.