I have a problem (actually a few of them) with KDE 3.3 on Centos 4.0.

I have my PC connected to a Belkin omniview soho kvm switch (with a PS2 keyboard and mouse and USB connection from the switch to pc).

If I switch over to my centos box from my windows machine then the scroll wheel on my mouse does not work properly. I cannot scroll and cannot 'cut and paste; with the scroll wheel. If I click in a window and then select my windows pc and then my centos pc again, then it works properly again.

Any ideas how to stop this?

Edit: Whoops, didn't see that it worked again after you switched back and forth. This may or may not help you. Sorry!

Your problems seems to be either a key-binding thing (your middle button works, Linux just doesn't know to copy/paste when you hit it), or an xorg thing. Your xorg.conf file (or xfree86's comparable one) has a little section on mice that looks like:

Section "InputDevice"

Identifier "Mouse0"
Driver "mouse"
Option "Protocol" "IMPS/2"
Option "Device" "/dev/input/mice"
Option "ZaxisMapping" "4 5"

What you would most likely need to add to get the mouse wheel working is that last line (possibly the third too)- you'd have to put it in your xorg.conf. It is usually located in /etc/X11/xorg.conf. I may be wrong on that location...I'm not at my Linux box right now.