Failed to find steam interface for CFileSystem_Steam

Hello,
For a few days I have this error and I don’t know what it is. I can’t run many mods on steam because of this error message. I am running on Windows 7 (x32) I never had this kind of errors. Also, I have looked for some duplicated “steam.dll” files and nothing found. Can anyone help me to solve this ? Why I have this error right now and not when I have made the installation ?
Thank you !

Error!
CFileSystem_Steam::Init() failed: failed to find steam interface
OK
