I also found that the whole AMX plug-in has to be installed in a sequential order to make it work .

I have to play the game (listen server, dedicated server, and regular game) with liblist.gam using gamedll dlls\mp.dll for the very first time (just once)

Then, replace the gamedll to addons\metamod\dlls\metamod.dll
to play the game without error messages. I don't know why, but it works for me........ ........

Weird.....how bizzard.....o_O