Intellimouse side buttons.
Try binding BUTTON4 and BUTTON5, and see if they work. If they do, then CTRL+C and CTRL+V may no longer be vaild binds, as they added a Copy and Paste function when Chat was revamped...

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what version intelli drivers are you using? - I know that they've recently been upgraded to version 8 and these solved a few niggly issues I had with my mouse (wireless 5000) and keyboard (wireless 3000 v2)
http://www.scene-and-heard.com/cov/covsig.jpg
I recently updated to Windows 7 from XP and now I can longer use the two side buttons on my MS Intellimouse with the current drivers. I have he left mapped to Copy (Ctrl + C) and the right mapped to Paste (Ctrl + V). I then keybind those combinations to Aoes and heals. It works in every program other than CoX.
I tried rolling back drivers to 4.0 but Win7 won't accept them.