ned's blog
Binding keys in Far Cry 2 multiplayer. 
First things first. Thanks to OS|Wendigo for posting a fix for this very annoying issue.

Many of us discovered that the key-binds we set up for singleplayer didn't work for the muliplayer part of the game. It appeared that you were forced to use the standard keys (defaults) if you wanted to play multiplayer. But, there is a way to sort this out.

-start the game
-login to multiplayer
-enter a server (probably easier to just create your own)
-go to options menu - controls
-select defaults and re-map your keys

Fix found at the Ubisoft forum - here -