mk47at: You might want to try adding something like "+seta sv_cheats 1" to the commandline options. I'm not really sure about the syntax...
Edit: I'm not talking about the ingame console, but the link target.
CrazyDiscoBall: I have tried that and it didn't work for me. I did what you said and I started the game. I immediately opened the command line and I saw for a brief second the command being read as sv_cheats = 1 but it then changed back to the default value of 0 and any attempt to change gives of the usual message about that command being read only.
I've done a quick search on the net and some people claim that sv_cheats gets set to 0 if you start a new game, but that the value isn't changed if you load a game. Have you tried to save the game, restart and load the save?
If it still doesn't work, I will look into it, tomorrow.
Edit:
I just gave it a quick test: I started the game with the default shortcut (without setting sv_cheats), started a new game, checked sv_cheats (it was 0), saved, returned to the main menu, checked sv_cheats (it was switched to 1 automatically), restored the game and sv_cheats was still 1.