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:
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.
Last edited by azucaro; 05-05-2005 at 12:45 PM.