Mega bump but I don't care.

I've finally decided to try to fix this properly, so I've completely reinstalled Steam and my games, but now I get a different error message (probably all mean the same thing) for each game I try to launch, for example when I launch CS:S I get 'Failed to load the launcher DLL: Invalid access to memory location' and for Bad Company 2 it says 'Battlefield Bad Company 2 failed to start (error code 66)'.

So yeah still just as bad as it was before, any ideas what those error messages mean?